4. Connecting to Oracle Database
Connections between python-oracledb and Oracle Database are used for executing SQL, PL/SQL, and SODA.
By default, python-oracledb runs in a ‘Thin’ mode which connects directly to Oracle Database. This mode does not need Oracle Client libraries. However, some additional functionality is available when python-oracledb uses them. Python-oracledb is said to be in ‘Thick’ mode when Oracle Client libraries are used. See Enabling python-oracledb Thick mode. Both modes have comprehensive functionality supporting the Python Database API v2.0 Specification.
This chapter covers python-oracledb’s synchronous programming model. For discussion of asynchronous programming, see Concurrent Programming with asyncio.
If you intend to use the Thick mode, then you must call
init_oracle_client() in the application before any standalone
connection or pool is created. The python-oracledb Thick mode loads Oracle
Client libraries which communicate over Oracle Net to an existing database.
The Oracle Client libraries need to be installed separately. See
Installing python-oracledb. Oracle Net is not a separate product: it is how the
Oracle Client and Oracle Database communicate.
There are two ways to create a connection to Oracle Database using python-oracledb:
Standalone connections: Standalone connections are useful when the application needs a single connection to a database. Connections are created by calling
oracledb.connect().Pooled connections: Connection pooling is important for performance when applications frequently connect and disconnect from the database. Pools support Oracle’s high availability features and are recommended for applications that must be reliable. Small pools can also be useful for applications that want a few connections available for infrequent use. Pools are created with
oracledb.create_pool()at application initialization time, and thenConnectionPool.acquire()can be called to obtain a connection from a pool.
Many connection behaviors can be controlled by python-oracledb connection options. Other settings can be configured in Optional Oracle Net Configuration Files or in Optional Oracle Client Configuration File. These include limiting the amount of time that opening a connection can take, or enabling network encryption.
Note
Creating a connection in python-oracledb Thin mode always requires a
connection string, or the database host name and service name, to be
specified. The Thin mode cannot use “bequeath” connections and does not
reference Oracle environment variables ORACLE_SID, TWO_TASK,
or LOCAL.
Note
When using python-oracledb in Thin mode, the tnsnames.ora file will not
be automatically located. The file’s directory must explicitly be passed
to the application, see Optional Oracle Net Configuration Files.
4.1. Standalone Connections
Standalone connections are database connections that do not use a
python-oracledb connection pool. They are useful for simple applications that
use a single connection to a database. Simple connections are created by
calling oracledb.connect() and passing a database username, the
database password for that user, and a ‘data source name’ connection
string. Python-oracledb also supports external authentication and so passwords do not need to be in the application.
4.1.1. Creating a Standalone Connection
Standalone connections are created by calling oracledb.connect().
A simple standalone connection example:
import oracledb
import getpass
userpwd = getpass.getpass("Enter password: ")
connection = oracledb.connect(user="hr", password=userpwd,
dsn="dbhost.example.com/orclpdb")
You could alternatively read the password from an environment variable:
userpwd = os.environ.get("PYTHON_PASSWORD")
connection = oracledb.connect(user="hr", password=userpwd,
dsn="localhost/orclpdb")
The oracledb.connect() method allows the database host name and
database service name to be passed as separate parameters. The database
listener port can also be passed:
import os
userpwd = os.environ.get("PYTHON_PASSWORD")
connection = oracledb.connect(user="hr", password=userpwd,
host="localhost", port=1521, service_name="orclpdb")
If you like to encapsulate values, parameters can be passed using a ConnectParams Object:
params = oracledb.ConnectParams(host="my_host", port=my_port, service_name="my_service_name")
conn = oracledb.connect(user="my_user", password="my_password", params=params)
Some values such as the database host name can be specified as connect()
parameters, as part of the connect string, and in the params object. If a
dsn is passed, the python-oracledb Thick mode will
use the dsn string to connect. Otherwise, a connection string is internally
constructed from the individual parameters and params object values, with
the individual parameters having precedence. In python-oracledb’s default Thin
mode, a connection string is internally used that contains all relevant values
specified. The precedence in Thin mode is that values in any dsn parameter
override values passed as individual parameters, which themselves override
values set in the params object. Similar precedence rules also apply to
other values.
A single, combined connection string can be passed to connect() but this
may cause complications if the password contains ‘@’ or ‘/’ characters:
username="hr"
userpwd = os.environ.get("PYTHON_PASSWORD")
host = "localhost"
port = 1521
service_name = "orclpdb"
dsn = f'{username}/{userpwd}@{host}:{port}/{service_name}'
connection = oracledb.connect(dsn)
4.1.1.1. Closing Connections
Connections should be released when they are no longer needed. You may prefer to let connections be automatically cleaned up when references to them go out of scope. This lets python-oracledb close dependent resources in the correct order:
with oracledb.connect(user="hr", password=userpwd,
dsn="dbhost.example.com/orclpdb") as connection:
with connection.cursor() as cursor:
cursor.execute("insert into SomeTable values (:1, :2)",
(1, "Some string"))
connection.commit()
This code ensures that once the block is completed, the connection is closed
and resources have been reclaimed by the database. In addition, any attempt to
use the variable connection outside of the block will simply fail.
Alternatively, you can explicitly close a connection by calling.
Connection.close():
connection = oracledb.connect(user="hr", password=userpwd, dsn="localhost/orclpdb")
# do something with the connection
. . .
# close the connection
connection.close()
4.1.2. Common Connection Errors
Some of the common connection errors that you may encounter in the python-oracledb’s default Thin mode are detailed below. Also see Error Handling in Thin and Thick Modes.
4.1.2.1. Use keyword parameters
If you use:
connection = oracledb.connect("hr", userpwd, "localhost/orclpdb")
then you will get the error:
TypeError: connect() takes from 0 to 1 positional arguments but 3 were given
The oracledb.connect() method requires keyword parameters to be used
connection = oracledb.connect(user="hr", password=userpwd, dsn="localhost/orclpdb")
The exception passing a single argument containing the combined credential and connection string. This is supported:
connection = oracledb.connect("hr/userpwd@localhost/orclpdb")
4.1.2.2. Use the correct credentials
If your username or password are not known by the database that you attempted to connect to, then you will get the error:
ORA-01017: invalid username/password; logon denied
Find the correct username and password and try reconnecting.
4.1.2.3. Use the correct connection string
If the hostname, port, or service name are incorrect, then the connection will fail with the error:
DPY-6001: cannot connect to database. Service "doesnotexist" is not
registered with the listener at host "localhost" port 1521. (Similar to
ORA-12514)
This error means that Python successfully reached a computer (in this case, “localhost” using the default port 1521) that is running a database. However, the database service you wanted (“doesnotexist”) does not exist there.
Technically, the error means the listener does not know about the service at the moment. So you might also get this error if the database is currently restarting.
This error is similar to the ORA-12514 error that you may see when connecting
with python-oracledb in Thick mode, or with some other Oracle tools.
The solution is to use a valid service name in the connection string. You can:
Check and fix any typos in the service name you used
Check if the hostname and port are correct
Ask your database administrator (DBA) for the correct values
Wait a few moments and re-try in case the database is restarting
Review the connection information in your cloud console or cloud wallet, if you are using a cloud database
Run lsnrctl status on the database machine to find the known service names
4.2. Connection Strings
The data source name parameter dsn of oracledb.connect() and
oracledb.create_pool() is the Oracle Database connection string
that identifies which database service to connect to. The dsn string can be
one of:
An Oracle Easy Connect string
An Oracle Net Connect Descriptor string
A Net Service Name mapping to a connect descriptor
For more information about naming methods, see Oracle Net Service Reference.
4.2.1. Easy Connect Syntax for Connection Strings
An Easy Connect string is often the simplest connection string to use for the
data source name parameter dsn of oracledb.connect() and
oracledb.create_pool(). This method does not need configuration files
such as tnsnames.ora.
For example, to connect to the Oracle Database service orclpdb that is
running on the host dbhost.example.com with the default Oracle
Database port 1521, use:
connection = oracledb.connect(user="hr", password=userpwd,
dsn="dbhost.example.com/orclpdb")
If the database is using a non-default port, it must be specified:
connection = oracledb.connect(user="hr", password=userpwd,
dsn="dbhost.example.com:1984/orclpdb")
The Easy Connect syntax supports Oracle Database service names. It cannot be used with the older System Identifiers (SID).
The latest Easy Connect Plus syntax allows the use of multiple hosts or ports, along with optional entries for the wallet location, the distinguished name of the database server, and even allows some network configuration options be set. This means that a sqlnet.ora file is not needed for some common connection scenarios. See Oracle’s Technical Paper on Easy Connect Plus Syntax for more information.
In python-oracledb Thin mode, any unknown Easy Connect options are ignored and are not passed to the database. See Connection String Differences for more information.
In python-oracledb Thick mode, it is the Oracle Client libraries that parse the Easy Connect string. Check the Easy Connect Naming method in Oracle Net Service Administrator’s Guide for the syntax to use in your version of the Oracle Client libraries.
4.2.2. Net Service Names for Connection Strings
Connect Descriptor Strings are commonly stored in a tnsnames.ora file and associated with a Net Service Name. This name can be
used directly for the data source name parameter dsn of
oracledb.connect() and oracledb.create_pool(). For example,
given a file /opt/oracle/config/tnsnames.ora with the following contents:
ORCLPDB =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = dbhost.example.com)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = orclpdb)
)
)
Then you could connect in python-oracledb Thin mode by using the following code:
connection = oracledb.connect(user="hr", password=userpwd, dsn="orclpdb",
config_dir="/opt/oracle/config")
More options for how python-oracledb locates tnsnames.ora files is detailed
in Optional Oracle Net Configuration Files. Note in python-oracledb Thick mode, the configuration
directory must be set during initialization, not at connection time.
For more information about Net Service Names, see Database Net Services Reference.
4.2.3. Oracle Net Connect Descriptor Strings
Full Connect Descriptor strings can be embedded directly in python-oracledb applications:
dsn = """(DESCRIPTION=
(FAILOVER=on)
(ADDRESS_LIST=
(ADDRESS=(PROTOCOL=tcp)(HOST=sales1-svr)(PORT=1521))
(ADDRESS=(PROTOCOL=tcp)(HOST=sales2-svr)(PORT=1521)))
(CONNECT_DATA=(SERVICE_NAME=sales.example.com)))"""
connection = oracledb.connect(user="hr", password=userpwd, dsn=dsn)
The oracledb.ConnectParams() and ConnectParams.get_connect_string()
functions can be used to construct a connect descriptor string from the
individual components, see Using the ConnectParams Builder Class. For example:
cp = oracledb.ConnectParams(host="dbhost.example.com", port=1521, service_name="orclpdb")
dsn = cp.get_connect_string()
print(dsn)
This prints:
(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=tcp)(HOST=dbhost.example.com)(PORT=1521)))(CONNECT_DATA=(SERVICE_NAME=orclpdb))(SECURITY=(SSL_SERVER_DN_MATCH=True)))
4.2.4. JDBC and Oracle SQL Developer Connection Strings
The python-oracledb connection string syntax is different from Java JDBC and the common Oracle SQL Developer syntax. If these JDBC connection strings reference a service name like:
jdbc:oracle:thin:@hostname:port/service_name
For example:
jdbc:oracle:thin:@dbhost.example.com:1521/orclpdb
then use Oracle’s Easy Connect syntax in python-oracledb:
connection = oracledb.connect(user="hr", password=userpwd,
dsn="dbhost.example.com:1521/orclpdb")
Alternatively, if a JDBC connection string uses an old-style Oracle Database SID “system identifier”, and the database does not have a service name:
jdbc:oracle:thin:@hostname:port:sid
For example:
jdbc:oracle:thin:@dbhost.example.com:1521:orcl
then connect by using the sid parameter:
connection = oracledb.connect(user="hr", password=userpwd,
host="dbhost.example.com", port=1521, sid="orcl")
Alternatively, create a tnsnames.ora (see Optional Oracle Net Configuration Files) entry, for
example:
finance =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = dbhost.example.com)(PORT = 1521))
(CONNECT_DATA =
(SID = ORCL)
)
)
This can be referenced in python-oracledb:
connection = oracledb.connect(user="hr", password=userpwd, dsn="finance")
4.3. Using the ConnectParams Builder Class
The ConnectParams class allows you to define connection
parameters in a single place. The oracledb.ConnectParams() function
returns a ConnectParams object. The object can be passed to
oracledb.connect(). For example:
cp = oracledb.ConnectParams(user="hr", password=userpwd,
host="dbhost", port=1521, service_name="orclpdb")
connection = oracledb.connect(params=cp)
The use of the ConnectParams class is optional because you can pass the same
parameters directly to connect(). For example, the code above
is equivalent to:
connection = oracledb.connect(user="hr", password=userpwd,
host="dbhost", port=1521, service_name="orclpdb")
If you want to keep credentials separate, you can use ConnectParams just to encapsulate connection string components:
cp = oracledb.ConnectParams(host="dbhost", port=1521, service_name="orclpdb")
connection = oracledb.connect(user="hr", password=userpwd, params=cp)
You can use ConnectParams.get_connect_string() to get a connection
string from a ConnectParams object:
cp = oracledb.ConnectParams(host="dbhost", port="my_port", service_name="my_service_name")
dsn = cp.get_connect_string()
connection = oracledb.connect(user="hr", password=userpwd, dsn=dsn)
To parse a connection string and store components as attributes:
cp = oracledb.ConnectParams()
cp.parse_connect_string("host.example.com:1522/orclpdb")
Most parameter values of oracledb.ConnectParams() are gettable as
attributes. For example, to get the stored host name:
print(cp.host)
Attributes such as the password are not gettable.
You can set individual default attributes using ConnectParams.set():
cp = oracledb.ConnectParams(host="localhost", port=1521, service_name="orclpdb")
# set a new port
cp.set(port=1522)
# change both the port and service name
cp.set(port=1523, service_name="orclpdb")
Note ConnectParams.set() has no effect after
ConnectParams.parse_connect_string() has been called.
Some values such as the database host name can be specified as
oracledb.connect(), parameters, as part of the connect string, and in
the params object. If a dsn is passed, the python-oracledb Thick mode will use the dsn string to connect. Otherwise, a
connection string is internally constructed from the individual parameters and
params object values, with the individual parameters having precedence. In
python-oracledb’s default Thin mode, a connection string is internally used
that contains all relevant values specified. The precedence in Thin mode is
that values in any dsn parameter override values passed as individual
parameters, which themselves override values set in the params object.
Similar precedence rules also apply to other values.
The ConnectParams.parse_dsn_with_credentials() can be used to extract
the username, password and connection string from a DSN:
cp = oracledb.ConnectParams()
(un,pw,cs) = cp.parse_dsn_with_credentials("scott/tiger@localhost/orclpdb")
Empty values are returned as None.
The ConnectParams.get_network_service_names() can be used to get a
list of the network service names that are defined in the
tnsnames.ora file. The directory that contains the
tnsnames.ora file can be specified in the config_dir
attribute.
cp = oracledb.ConnectParams(host="my_host", port=my_port, dsn="orclpdb",
config_dir="/opt/oracle/config")
cp.get_network_service_names()
If the ConnectParams.get_network_service_names() method is called but
a tnsnames.ora file does not exist, then an error such as the following is
returned:
DPY-4026: file tnsnames.ora not found in /opt/oracle/config
If config_dir is not specified, then the following
error is returned:
DPY-4027: no configuration directory to search for tnsnames.ora
When creating a standalone connection or connection pool the equivalent
internal extraction is done automatically when a value is passed to the dsn
parameter of oracledb.connect() or oracledb.create_pool() but
no value is passed to the user password.
4.4. Connection Pooling
Python-oracledb’s connection pooling lets applications create and maintain a pool of open connections to the database. Connection pooling is available in both Thin and Thick modes. Connection pooling is important for performance and scalability when applications need to handle a large number of users who do database work for short periods of time but have relatively long periods when the connections are not needed. The high availability features of pools also make small pools useful for applications that want a few connections available for infrequent use and requires them to be immediately usable when acquired. Applications that would benefit from connection pooling but are too difficult to modify from the use of standalone connections can take advantage of Implicit Connection Pooling with DRCP and PRCP.
In python-oracledb Thick mode, the pool implementation uses Oracle’s session pool technology which supports additional Oracle Database features, for example some advanced high availability features.
4.4.1. Creating a Connection Pool
A connection pool is created by calling oracledb.create_pool().
Various pool options can be specified as described in
create_pool() and detailed below.
For example, to create a pool that initially contains one connection but can grow up to five connections:
pool = oracledb.create_pool(user="hr", password=userpwd, dsn="dbhost.example.com/orclpdb",
min=1, max=5, increment=1)
After the pool has been created, your application can get a connection from
it by calling ConnectionPool.acquire():
connection = pool.acquire()
These connections can be used in the same way that Standalone Connections are used.
By default, acquire() calls wait for a connection
to be available before returning to the application. A connection will be
available if the pool currently has idle connections, when another user
returns a connection to the pool, or after the pool grows. Waiting allows
applications to be resilient to temporary spikes in connection load. Users
may have to wait a brief time to get a connection but will not experience
connection failures.
You can change the behavior of acquire() by setting the
getmode option during pool creation. For example, the option can be
set so that if all the connections are currently in use by the application, any
additional acquire() call will return an error
immediately.
pool = oracledb.create_pool(user="hr", password=userpwd, dsn="dbhost.example.com/orclpdb",
min=2, max=5, increment=1,
getmode=oracledb.POOL_GETMODE_NOWAIT)
Note that when using this option value in Thick mode with Oracle Client
libraries 12.2 or earlier, the acquire() call will
still wait if the pool can grow. However, you will get an error immediately if
the pool is at its maximum size. With newer Oracle Client libraries and with
Thin mode, an error will be returned if the pool has to, or cannot, grow.
When your application has finished performing all required database operations,
the pooled connection should be released to make it available for other users
of the pool. You can do this with ConnectionPool.release() or
Connection.close(). Alternatively you may prefer to let pooled
connections be closed implicitly at the end of scope. For example, by using a
with statement:
with pool.acquire() as connection:
with connection.cursor() as cursor:
for result in cursor.execute("select * from mytab"):
print(result)
At application shutdown, the connection pool can be completely closed using
ConnectionPool.close():
pool.close()
To force immediate pool termination when connections are still in use, execute:
pool.close(force=True)
See connection_pool.py for a runnable example of connection pooling.
Connection Pool Growth
At pool creation, min connections are established to the database. When a
pool needs to grow, new connections are created automatically limited by the
max size. The pool max size restricts the number of application users
that can do work in parallel on the database.
The number of connections opened by a pool can shown with the attribute.
ConnectionPool.opened. The number of connections the application has
obtained with acquire() can be shown with
ConnectionPool.busy. The difference in values is the number of
connections unused or ‘idle’ in the pool. These idle connections may be
candidates for the pool to close, depending on the pool configuration.
Pool growth is normally initiated when acquire() is
called and there are no idle connections in the pool that can be returned to
the application. The number of new connections created internally will be the
value of the create_pool() parameter increment.
Depending on whether Thin or Thick mode is used and on the pool creation
getmode value that is set, any acquire() call that
initiates pool growth may wait until all increment new connections are
internally opened. However, in this case the cost is amortized because later
acquire() calls may not have to wait and can
immediately return an available connection. Some users set larger
increment values even for fixed-size pools because it can help a pool
re-establish itself if all connections become invalid, for example after a
network dropout. In the common case of Thin mode with the default getmode
of POOL_GETMODE_WAIT, any acquire() call that
initiates pool growth will return after the first new connection is created,
regardless of how big increment is. The pool will then continue to
re-establish connections in a background thread.
A connection pool can shrink back to its minimum size min when connections
opened by the pool are not used by the application. This frees up database
resources while allowing pools to retain connections for active users. If
connections are idle in the pool (i.e. not currently acquired by the
application) and are unused for longer than the pool creation attribute
timeout value, then they will be closed. The check occurs every
timeout interval and hence in the worst case it may take twice the
timeout time to close the idle connections. The default timeout is 0
seconds signifying an infinite time and meaning idle connections will never be
closed.
In python-oracledb Thick mode, the pool creation parameter
max_lifetime_session also allows pools to shrink. This parameter bounds
the total length of time that a connection can exist starting from the time the
pool created it. If a connection was created max_lifetime_session or
longer seconds ago, then it will be closed when it is idle in the pool. In the
case when timeout and max_lifetime_session are both set, the connection
will be terminated if either the idle timeout happens or the max lifetime
setting is exceeded. Note that when using python-oracledb in Thick mode with
Oracle Client libraries prior to 21c, pool shrinkage is only initiated when the
pool is accessed so pools in fully dormant applications will not shrink until
the application is next used.
For pools created with external authentication, with
homogeneous set to False, or when using Database Resident Connection Pooling (DRCP),
then the number of connections opened at pool creation is zero even if a larger
value is specified for min. Also, in these cases the pool increment unit
is always 1 regardless of the value of increment.
Pool Connection Health
Before ConnectionPool.acquire() returns, python-oracledb does a
lightweight check similar to Connection.is_healthy() to see if the
network transport for the selected connection is still open. If it is not,
then acquire() will clean up the connection and return
a different one.
This check will not detect cases such as where the database session has been
terminated by the DBA, or reached a database resource manager quota limit. To
help in those cases, acquire() will also do a full
round-trip database ping similar to
Connection.ping() when it is about to return a connection that was idle
in the pool (i.e. not currently acquired by the application) for
ConnectionPool.ping_interval seconds. If the ping fails, the
connection will be discarded and another one obtained before
acquire() returns to the application.
Because this full ping is time based and may not occur for each
acquire(), the application may still get an unusable
connection. Also, network timeouts and session termination may occur between
the calls to acquire() and Cursor.execute().
To handle these cases, applications need to check for errors after each
execute() and make application-specific decisions about
retrying work if there was a connection failure. When using python-oracledb in
Thick mode, Oracle Database features like Application Continuity can do this automatically in some cases.
You can explicitly initiate a full round-trip ping at any time with
Connection.ping() to check connection liveness but the overuse will
impact performance and scalability.
Ensure that the firewall, resource manager or user profile IDLE_TIME do not expire idle sessions, since this will require connections to be recreated which will impact performance and scalability.
A pool’s internal connection re-establishment after lightweight and full pings can mask performance-impacting configuration issues such as firewalls terminating connections. You should monitor AWR reports for an unexpectedly large connection rate.
4.4.2. Connection Pool Sizing
The Oracle Real-World Performance Group’s recommendation is to use fixed size
connection pools. The values of min and max should be the same. When
using older versions of Oracle Client libraries the increment parameter
will need to be zero (which is internally treated as a value of one), but
otherwise you may prefer a larger size since this will affect how the
connection pool is re-established after, for example, a network dropout
invalidates all connections.
Fixed size pools avoid connection storms on the database which can decrease
throughput. See Guideline for Preventing Connection Storms: Use Static Pools,
which contains more details about sizing of pools. Having a fixed size will
also guarantee that the database can handle the upper pool size. For example,
if a dynamically sized pool needs to grow but the database resources are
limited, then ConnectionPool.acquire() may return errors such as
ORA-28547. With a fixed pool size, this class of error will occur when the
pool is created, allowing you to change the pool size or reconfigure the
database before users access the application. With a dynamically growing pool,
the error may occur much later while the application is in use.
The Real-World Performance Group also recommends keeping pool sizes small because they may perform better than larger pools. The pool attributes should be adjusted to handle the desired workload within the bounds of available resources in python-oracledb and the database.
4.4.3. Connection Pool Reconfiguration
Some pool settings can be changed dynamically with
ConnectionPool.reconfigure(). This allows the pool size and other
attributes to be changed during application runtime without needing to restart
the pool or application.
For example a pool’s size can be changed like:
pool.reconfigure(min=10, max=10, increment=0)
After any size change has been processed, reconfiguration on the other parameters is done sequentially. If an error such as an invalid value occurs when changing one attribute, then an exception will be generated but any already changed attributes will retain their new values.
During reconfiguration of a pool’s size, the behavior of
ConnectionPool.acquire() depends on the pool creation getmode value
in effect when acquire() is called, see
ConnectionPool.reconfigure(). Closing connections or closing the pool
will wait until after pool reconfiguration is complete.
Calling reconfigure() is the only way to change a pool’s min, max
and increment values. Other attributes such as
wait_timeout can be passed to reconfigure() or they
can be set directly, for example:
pool.wait_timeout = 1000
4.4.4. Session Callbacks for Setting Pooled Connection State
Applications can set “session” state in each connection. Examples of session
state are NLS globalization settings from ALTER SESSION statements. Pooled
connections will retain their session state after they have been released back
to the pool. However, because pools can grow or connections in the pool can
be recreated, there is no guarantee a subsequent
acquire() call will return a database connection that
has any particular state.
The create_pool() parameter session_callback enables
efficient setting of session state so that connections have a known session
state, without requiring that state to be explicitly set after every
acquire() call. The callback is internally invoked
when acquire() is called and runs first.
The session callback can be a Python function or a PL/SQL procedure.
Connections can also be tagged when they are released back to the pool. The tag is a user-defined string that represents the session state of the connection. When acquiring connections, a particular tag can be requested. If a connection with that tag is available, it will be returned. If not, then another session will be returned. By comparing the actual and requested tags, applications can determine what exact state a session has, and make any necessary changes.
Connection tagging and PL/SQL callbacks are only available in python-oracledb Thick mode. Python callbacks can be used in python-oracledb Thin and Thick modes.
There are three common scenarios for session_callback:
When all connections in the pool should have the same state, use a Python callback without tagging.
When connections in the pool require different state for different users, use a Python callback with tagging.
With Database Resident Connection Pooling (DRCP), use a PL/SQL callback with tagging.
4.4.4.1. Python Callback
If the session_callback parameter is a Python procedure, it will be called
whenever acquire() will return a newly created database
connection that has not been used before. It is also called when connection
tagging is being used and the requested tag is not identical to the tag in the
connection returned by the pool.
An example is:
# Set the NLS_DATE_FORMAT for a session
def init_session(connection, requested_tag):
with connection.cursor() as cursor:
cursor.execute("alter session set nls_date_format = 'YYYY-MM-DD HH24:MI'")
# Create the pool with session callback defined
pool = oracledb.create_pool(user="hr", password=userpwd, dsn="localhost/orclpdb",
session_callback=init_session)
# Acquire a connection from the pool (will always have the new date format)
connection = pool.acquire()
If needed, the init_session() procedure is called internally before
acquire() returns. It will not be called when
previously used connections are returned from the pool. This means that the
ALTER SESSION does not need to be executed after every
acquire() call. This improves performance and
scalability.
In this example tagging was not being used, so the requested_tag parameter
is ignored.
Note that if you need to execute multiple SQL statements in the callback, use an
anonymous PL/SQL block to save round-trips of repeated
execute() calls. With ALTER SESSION, pass multiple settings in the one
statement:
cursor.execute("""
begin
execute immediate
'alter session set nls_date_format = ''YYYY-MM-DD''
nls_language = AMERICAN';
-- other SQL statements could be put here
end;""")
4.4.4.2. Connection Tagging
Connection tagging is used when connections in a pool should have differing
session states. In order to retrieve a connection with a desired state, the
tag attribute in acquire() needs to be set.
Note
Connection tagging is only supported in the python-oracledb Thick mode. See Enabling python-oracledb Thick mode .
When python-oracledb is using Oracle Client libraries 12.2 or later, then
python-oracledb uses ‘multi-property tags’ and the tag string must be of the
form of one or more “name=value” pairs separated by a semi-colon, for example
"loc=uk;lang=cy".
When a connection is requested with a given tag, and a connection with that tag
is not present in the pool, then a new connection, or an existing connection
with cleaned session state, will be chosen by the pool and the session callback
procedure will be invoked. The callback can then set desired session state and
update the connection’s tag. However, if the matchanytag parameter of
acquire() is True, then any other tagged connection may
be chosen by the pool and the callback procedure should parse the actual and
requested tags to determine which bits of session state should be reset.
The example below demonstrates connection tagging:
def init_session(connection, requested_tag):
if requested_tag == "NLS_DATE_FORMAT=SIMPLE":
sql = "ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD'"
elif requested_tag == "NLS_DATE_FORMAT=FULL":
sql = "ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI'"
cursor = connection.cursor()
cursor.execute(sql)
connection.tag = requested_tag
pool = oracledb.create_pool(user="hr", password=userpwd, dsn="orclpdb",
session_callback=init_session)
# Two connections with different session state:
connection1 = pool.acquire(tag="NLS_DATE_FORMAT=SIMPLE")
connection2 = pool.acquire(tag="NLS_DATE_FORMAT=FULL")
See session_callback.py for an example.
4.4.4.3. PL/SQL Callback
Note
PL/SQL Callbacks are only supported in the python-oracledb Thick mode. See Enabling python-oracledb Thick mode.
When python-oracledb uses Oracle Client 12.2 or later, the session callback can also be the name of a PL/SQL procedure. A PL/SQL callback will be initiated only when the tag currently associated with a connection does not match the tag that is requested. A PL/SQL callback is most useful when using Database Resident Connection Pooling (DRCP) because DRCP does not require a round-trip to invoke a PL/SQL session callback procedure.
The PL/SQL session callback should accept two VARCHAR2 arguments:
PROCEDURE myPlsqlCallback (
requestedTag IN VARCHAR2,
actualTag IN VARCHAR2
);
The logic in this procedure can parse the actual tag in the session that has
been selected by the pool and compare it with the tag requested by the
application. The procedure can then change any state required before the
connection is returned to the application from
acquire().
If the matchanytag attribute of acquire() is
True, then a connection with any state may be chosen by the pool.
Oracle ‘multi-property tags’ must be used. The tag string must be of the form
of one or more “name=value” pairs separated by a semi-colon, for example
"loc=uk;lang=cy".
In python-oracledb set session_callback to the name of the PL/SQL
procedure. For example:
pool = oracledb.create_pool(user="hr", password=userpwd,
dsn="dbhost.example.com/orclpdb:pooled",
session_callback="MyPlsqlCallback")
connection = pool.acquire(tag="NLS_DATE_FORMAT=SIMPLE",
# DRCP options, if you are using DRCP
cclass='MYCLASS',
purity=oracledb.PURITY_SELF)
See session_callback_plsql.py for an example.
4.4.5. Heterogeneous and Homogeneous Connection Pools
By default, connection pools are ‘homogeneous’, meaning that all connections use the same database credentials. Both python-oracledb Thin and Thick modes support homogeneous pools.
Creating Heterogeneous Pools
The python-oracledb Thick mode additionally supports Heterogeneous pools,
allowing different user names and passwords to be passed to each
acquire() call.
To create an heterogeneous pool, set the create_pool()
parameter homogeneous to False:
pool = oracledb.create_pool(dsn="dbhost.example.com/orclpdb", homogeneous=False)
connection = pool.acquire(user="hr", password=userpwd)
4.4.6. Using the PoolParams Builder Class
The PoolParams class allows you to define connection and
pool parameters in a single place. The oracledb.PoolParams() function
returns a PoolParams object. This is a subclass of the ConnectParams
class with additional pool-specific attributes such as the pool
size. A PoolParams object can be passed to
oracledb.create_pool(). For example:
pp = oracledb.PoolParams(min=1, max=2, increment=1)
pool = oracledb.create_pool(user="hr", password=userpw, dsn="dbhost.example.com/orclpdb",
params=pp)
The use of the PoolParams class is optional because you can pass the same
parameters directly to create_pool(). For example, the code
above is equivalent to:
pool = oracledb.create_pool(user="hr", password=userpw, dsn="dbhost.example.com/orclpdb",
min=1, max=2, increment=1)
Most PoolParams arguments are gettable as properties. They may be set
individually using the set() method:
pp = oracledb.PoolParams()
pp.set(min=5)
print(pp.min) # 5
Some values such as the database host name, can be specified as
oracledb.create_pool() parameters, as part of the connect string, and
in the params object. If a dsn is passed, the python-oracledb
Thick mode will use the dsn string to connect.
Otherwise, a connection string is internally constructed from the individual
parameters and params object values, with the individual parameters having
precedence. In python-oracledb’s default Thin mode, a connection string is
internally used that contains all relevant values specified. The precedence in
Thin mode is that values in any dsn parameter override values passed as
individual parameters, which themselves override values set in the params
object. Similar precedence rules also apply to other values.
4.5. Database Resident Connection Pooling (DRCP)
Database Resident Connection Pooling (DRCP) enables database resource sharing for applications which use a large number of connections that run in multiple client processes or run on multiple middle-tier application servers. By default, each connection from Python will use one database server process. DRCP allows pooling of these server processes. This reduces the amount of memory required on the database host. The DRCP pool can be shared by multiple applications.
DRCP is useful for applications which share the same database credentials, have similar session settings (for example date format settings or PL/SQL package state), and where the application gets a database connection, works on it for a relatively short duration, and then releases it.
For efficiency, it is recommended that DRCP connections should be used in conjunction with python-oracledb’s local connection pool. However, although using DRCP with standalone connections is not as efficient it does allow the database to reuse database server processes which can provide a performance benefit for applications that cannot use a local connection pool.
Although applications can choose whether or not to use pooled connections at runtime, care must be taken to configure the database appropriately for the number of expected connections, and also to stop inadvertent use of non-DRCP connections leading to a database server resource shortage. Conversely, avoid using DRCP connections for long-running operations.
For more information about DRCP, see Oracle Database Concepts Guide and for DRCP Configuration, see Oracle Database Administrator’s Guide.
Using DRCP with python-oracledb applications involves the following steps:
Configuring and enabling DRCP in the database
Configuring the application to use a DRCP connection
Deploying the application
4.5.1. Enabling DRCP in Oracle Database
Every Oracle Database uses a single, default DRCP connection pool. From Oracle Database 21c, each pluggable database can optionally have its own pool. Note that DRCP is already enabled in Oracle Autonomous Database and pool management is different to the steps below.
DRCP pools can be configured and administered by a DBA using the
DBMS_CONNECTION_POOL package:
EXECUTE DBMS_CONNECTION_POOL.CONFIGURE_POOL(
pool_name => 'SYS_DEFAULT_CONNECTION_POOL',
minsize => 4,
maxsize => 40,
incrsize => 2,
session_cached_cursors => 20,
inactivity_timeout => 300,
max_think_time => 600,
max_use_session => 500000,
max_lifetime_session => 86400)
Alternatively, the method DBMS_CONNECTION_POOL.ALTER_PARAM() can
set a single parameter:
EXECUTE DBMS_CONNECTION_POOL.ALTER_PARAM(
pool_name => 'SYS_DEFAULT_CONNECTION_POOL',
param_name => 'MAX_THINK_TIME',
param_value => '1200')
The inactivity_timeout setting terminates idle pooled servers, helping
optimize database resources. To avoid pooled servers permanently being held
onto by a selfish Python script, the max_think_time parameter can be set.
The parameters num_cbrok and maxconn_cbrok can be used to distribute
the persistent connections from the clients across multiple brokers. This may
be needed in cases where the operating system per-process descriptor limit is
small. Some customers have found that having several connection brokers
improves performance. The max_use_session and max_lifetime_session
parameters help protect against any unforeseen problems affecting server
processes. The default values will be suitable for most users. See the
Oracle DRCP documentation for details on parameters.
In general, if pool parameters are changed, then the pool should be restarted. Otherwise, server processes will continue to use old settings.
There is a DBMS_CONNECTION_POOL.RESTORE_DEFAULTS() procedure to
reset all values.
When DRCP is used with RAC, each database instance has its own connection
broker and pool of servers. Each pool has the identical configuration. For
example, all pools start with minsize server processes. A single
DBMS_CONNECTION_POOL command will alter the pool of each instance at the same
time. The pool needs to be started before connection requests begin. The
command below does this by bringing up the broker, which registers itself with
the database listener:
EXECUTE DBMS_CONNECTION_POOL.START_POOL()
Once enabled this way, the pool automatically restarts when the database
instance restarts, unless explicitly stopped with the
DBMS_CONNECTION_POOL.STOP_POOL() command:
EXECUTE DBMS_CONNECTION_POOL.STOP_POOL()
The pool cannot be stopped while connections are open.
4.5.2. Coding Applications to use DRCP
To use DRCP, application connection establishment must request a DRCP pooled server. The best practice is also to specify a user-chosen connection class name when creating a connection pool. A ‘purity’ of the connection session state can optionally be specified. See the Oracle Database documentation on benefiting from scalability for more information on purity and connection classes.
Requesting a Pooled Server
To request a DRCP pooled server, you can:
Use a specific connection string in
oracledb.create_pool()ororacledb.connect(). For example with the Easy Connect syntax:pool = oracledb.create_pool(user="hr", password=userpwd, dsn="dbhost.example.com/orclpdb:pooled", min=2, max=5, increment=1, cclass="MYAPP")
Alternatively, add
(SERVER=POOLED)to the connect descriptor such as used in an Oracle Network configuration filetnsnames.ora:customerpool = (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp) (HOST=dbhost.example.com) (PORT=1521))(CONNECT_DATA=(SERVICE_NAME=CUSTOMER) (SERVER=POOLED)))
Another way to use a DRCP pooled server is to set the
server_typeparameter during standalone connection creation or python-oracledb connection pool creation. For example:pool = oracledb.create_pool(user="hr", password=userpwd, dsn="dbhost.example.com/orclpdb", min=2, max=5, increment=1, server_type="pooled", cclass="MYAPP")
DRCP Connection Class Names
The best practice is to specify a cclass class name when creating a
python-oracledb connection pool. This user-chosen name provides some
partitioning of DRCP session memory so reuse is limited to similar
applications. It provides maximum pool sharing if multiple application
processes are started. A class name also allows better DRCP usage tracking in
the database. In the database monitoring views, the class name shown will be
the value specified in the application prefixed with the user name.
If cclass was not specified during pool creation, then the python-oracledb
Thin mode generates a unique connection class with the prefix “DPY” while the
Thick mode generates a unique connection class with the prefix “OCI”.
To create a connection pool requesting a DRCP pooled server and specifying a class name, you can call:
pool = oracledb.create_pool(user="hr", password=userpwd, dsn="dbhost.example.com/orclpdb:pooled",
min=2, max=5, increment=1,
cclass="MYAPP")
Once the pool has been created, your application can get a connection from it by calling:
connection = pool.acquire()
The python-oracledb connection pool size does not need to match the DRCP pool size. The limit on overall execution parallelism is determined by the DRCP pool size.
Connection class names can also be passed to acquire(),
if you want to use a connection with a different class:
pool = oracledb.create_pool(user="hr", password=userpwd, dsn="dbhost.example.com/orclpdb:pooled",
min=2, max=5, increment=1,
cclass="MYAPP")
connection = mypool.acquire(cclass="OTHERAPP")
If a pooled server of a requested class is not available, a server with new session state is used. If the DRCP pool cannot grow, a server with a different class may be used and its session state cleared.
If cclass is not set, then the pooled server sessions will not be reused
optimally, and the DRCP statistic views may record large values for NUM_MISSES.
DRCP Connection Purity
DRCP allows the connection session memory to be reused or cleaned each time a
connection is acquired from the pool. The pool or connection creation
purity parameter can be one of PURITY_NEW, PURITY_SELF, or
PURITY_DEFAULT. The value PURITY_SELF allows reuse of both the pooled
server process and session memory, giving maximum benefit from DRCP. By
default, python-oracledb pooled connections use PURITY_SELF and standalone
connections use PURITY_NEW.
To limit session sharing, you can explicitly require that new session memory be
allocated each time acquire() is called:
pool = oracledb.create_pool(user="hr", password=userpwd, dsn="dbhost.example.com/orclpdb:pooled",
min=2, max=5, increment=1,
cclass="MYAPP", purity=oracledb.PURITY_NEW)
Setting the Connection Class and Purity in the Connection String
Using python-oracledb Thin mode with Oracle Database 21c, you can specify the class and purity in the connection string itself. This removes the need to modify an existing application when you want to use DRCP:
dsn = "localhost/orclpdb:pooled?pool_connection_class=MYAPP&pool_purity=self"
For python-oracledb Thick mode, this syntax is supported if you are using Oracle Database 21c and Oracle Client 19c (or later). However, explicitly specifying the purity as SELF in this way may cause some unusable connections in a python-oracledb Thick mode connection pool to not be terminated. In summary, if you cannot programmatically set the class name and purity, or cannot use python-oracledb Thin mode, then avoid explicitly setting the purity as a connection string parameter when using a python-oracledb connection pooling in Thick mode.
Closing Connections when using DRCP
Similar to using a python-oracledb connection pool, Python scripts where
python-oracledb connections do not go out of scope quickly (which releases
them), or do not currently use Connection.close() or
ConnectionPool.release() should be examined to see if the connections
can be closed earlier. This allows maximum reuse of DRCP pooled servers by
other users:
pool = oracledb.create_pool(user="hr", password=userpwd, dsn="dbhost.example.com/orclpdb:pooled",
min=2, max=5, increment=1,
cclass="MYAPP")
# Do some database operations
connection = mypool.acquire()
. . .
connection.close(); # <- Add this to release the DRCP pooled server
# Do lots of non-database work
. . .
# Do some more database operations
connection = mypool.acquire() # <- And get a new pooled server only when needed
. . .
connection.close();
See drcp_pool.py for a runnable example of DRCP.
4.5.3. Monitoring DRCP
Data dictionary views are available to monitor the performance of DRCP. Database administrators can check statistics such as the number of busy and free servers, and the number of hits and misses in the pool against the total number of requests from clients. The views include:
DBA_CPOOL_INFOV$PROCESSV$SESSIONV$CPOOL_STATSV$CPOOL_CC_STATSV$CPOOL_CONN_INFO
DBA_CPOOL_INFO View
DBA_CPOOL_INFO displays configuration information about the DRCP pool. The
columns are equivalent to the dbms_connection_pool.configure_pool()
settings described in the table of DRCP configuration options, with the
addition of a STATUS column. The status is ACTIVE if the pool has been
started and INACTIVE otherwise. Note that the pool name column is called
CONNECTION_POOL. This example checks whether the pool has been started and
finds the maximum number of pooled servers:
SQL> SELECT connection_pool, status, maxsize FROM dba_cpool_info;
CONNECTION_POOL STATUS MAXSIZE
---------------------------- ---------- ----------
SYS_DEFAULT_CONNECTION_POOL ACTIVE 40
V$PROCESS and V$SESSION Views
The V$SESSION view shows information about the currently active DRCP
sessions. It can also be joined with V$PROCESS through
V$SESSION.PADDR = V$PROCESS.ADDR to correlate the views.
V$CPOOL_STATS View
The V$CPOOL_STATS view displays information about the DRCP statistics for
an instance. The V$CPOOL_STATS view can be used to assess how efficient the
pool settings are. This example query shows an application using the pool
effectively. The low number of misses indicates that servers and sessions were
reused. The wait count shows just over 1% of requests had to wait for a pooled
server to become available:
NUM_REQUESTS NUM_HITS NUM_MISSES NUM_WAITS
------------ ---------- ---------- ----------
10031 99990 40 1055
If cclass was set (allowing pooled servers and sessions to be
reused), then NUM_MISSES will be low. If the pool maxsize is too small for
the connection load, then NUM_WAITS will be high.
V$CPOOL_CC_STATS View
The view V$CPOOL_CC_STATS displays information about the connection class
level statistics for the pool per instance:
SQL> SELECT cclass_name, num_requests, num_hits, num_misses
FROM v$cpool_cc_stats;
CCLASS_NAME NUM_REQUESTS NUM_HITS NUM_MISSES
-------------------------------- ------------ ---------- ----------
HR.MYCLASS 100031 99993 38
The class name columns shows the database user name appended with the connection class name.
V$CPOOL_CONN_INFO View
The V$POOL_CONN_INFO view gives insight into client processes that are
connected to the connection broker, making it easier to monitor and trace
applications that are currently using pooled servers or are idle. This view was
introduced in Oracle 11gR2.
You can monitor the view V$CPOOL_CONN_INFO to, for example, identify
misconfigured machines that do not have the connection class set correctly.
This view maps the machine name to the class name. In python-oracledb Thick
mode, the class name will be default to one like shown below:
SQL> SELECT cclass_name, machine FROM v$cpool_conn_info;
CCLASS_NAME MACHINE
--------------------------------------- ------------
CJ.OCI:SP:wshbIFDtb7rgQwMyuYvodA cjlinux
In this example, you would examine applications on cjlinux and make them
set cclass.
When connecting to Oracle Autonomous Database on shared infrastructure (ADB-S),
the V$CPOOL_CONN_INFO view can be used to track the number of connection
hits and misses to show the pool efficiency.
4.5.4. Implicit Connection Pooling with DRCP and PRCP
Starting from Oracle Database 23c, Python applications that use DRCP and Oracle Connection Manager in Traffic Director Mode’s (CMAN-TDM) pooling capability Proxy Resident Connection Pooling (PRCP) can enable implicit connection pooling with DRCP and PRCP. For more information on PRCP, see the Oracle technical brief CMAN-TDM — An Oracle Database connection proxy for scalable and highly available applications.
With implicit connection pooling, applications do not need to explicitly close or release a connection to return the connection back to the DRCP or PRCP pool. Applications that do not use client-side connection pooling can take advantage of the implicit connection pooling feature with either Thin or Thick mode. Thick mode requires Oracle 23c Client libraries for implicit connection pooling support. Thin mode works with implicit connection pooling from python-oracledb 2.1 onwards.
Implicit connection pooling uses two types of boundary values to determine
when connections should be released back to the DRCP or PRCP pool. The
boundary value can be specified in the pool_boundary parameter as detailed
below. The two boundary values which can be
specified in the pool_boundary parameter are:
statement: If this boundary is specified, then the connection is released back to the DRCP or PRCP connection pool when the connection is implicitly stateless. A connection is implicitly stateless when there are no active cursors in the connection (that is, all the rows of the cursors have been internally fetched), no active transactions, no temporary tables, and no temporary LOBs.
transaction: If this boundary is specified, then the connection is released back to the DRCP or PRCP connection pool when either one of the methods
Connection.commit()orConnection.rollback()are called. It is recommended to not set theConnection.autocommitattribute to true when using implicit connection pooling. If you do set this attribute, then you will be unable to:Fetch any data that requires multiple round-trips to the database
To use implicit connection pooling in python-oracledb:
Enable the DRCP pool in the database. For example in SQL*Plus:
SQL> EXECUTE DBMS_CONNECTION_POOL.START_POOL();Specify to use a pooled server in:
The
dsnparameter oforacledb.connect()ororacledb.create_pool(). For example with the Easy Connect syntax:pool = oracledb.create_pool(user="hr", password=userpwd, dsn="dbhost.example.com/orclpdb:pooled", min=2, max=5, increment=1, cclass="MYAPP")
Or in the connect descriptor used in an Oracle Network configuration file such as tnsnames.ora by adding
(SERVER=POOLED). For example:customerpool = (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp) (HOST=dbhost.example.com) (PORT=1521))(CONNECT_DATA=(SERVICE_NAME=CUSTOMER) (SERVER=POOLED)))
Or in the
server_typeparameter duringstandalone connection creationorconnection pool creation. For example:pool = oracledb.create_pool(user="hr", password=userpwd, host="dbhost.example.com", service_name="orclpdb", min=2, max=5, increment=1, server_type="pooled", cclass="MYAPP")
Set the pool boundary to either statement or transaction in:
The Easy Connect string. For example, to use the statement boundary:
dsn = "localhost:1521/orclpdb:pooled?pool_boundary=statement"
Or the
CONNECT_DATAsection of the Connect Descriptor string. For example, to use the transaction boundary:tnsalias = (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=mymachine.example.com) (PORT=1521))(CONNECT_DATA=(SERVICE_NAME=orcl) (SERVER=POOLED)(POOL_BOUNDARY=TRANSACTION)))
Or the
pool_boundaryparameter inoracledb.connect()ororacledb.create_pool()
Note
Implicit connection pooling is disabled if the application sets the
pool_boundaryattribute to transaction or statement but does not specify to use a pooled server.For all the
POOL_BOUNDARYoptions, the default purity is set to SELF. You can specify the purity using thePOOL_PURITYparameter in the connection string to override the default purity value.
Note that it is recommended to use python-oracledb’s local Connection Pooling over implicit connection pooling.
4.6. Connecting Using Proxy Authentication
Proxy authentication allows a user (the “session user”) to connect to Oracle Database using the credentials of a “proxy user”. Statements will run as the session user. Proxy authentication is generally used in three-tier applications where one user owns the schema while multiple end-users access the data. For more information about proxy authentication, see the Oracle documentation.
An alternative to using proxy users is to set
Connection.client_identifier after connecting and use its value in
statements and in the database, for example for monitoring.
The following proxy examples use these schemas. The mysessionuser schema is
granted access to use the password of myproxyuser:
CREATE USER myproxyuser IDENTIFIED BY myproxyuserpw;
GRANT CREATE SESSION TO myproxyuser;
CREATE USER mysessionuser IDENTIFIED BY itdoesntmatter;
GRANT CREATE SESSION TO mysessionuser;
ALTER USER mysessionuser GRANT CONNECT THROUGH myproxyuser;
After connecting to the database, the following query can be used to show the session and proxy users:
SELECT SYS_CONTEXT('USERENV', 'PROXY_USER'),
SYS_CONTEXT('USERENV', 'SESSION_USER')
FROM DUAL;
Standalone connection examples:
# Basic Authentication without a proxy
connection = oracledb.connect(user="myproxyuser", password="myproxyuserpw",
dsn="dbhost.example.com/orclpdb")
# PROXY_USER: None
# SESSION_USER: MYPROXYUSER
# Basic Authentication with a proxy
connection = oracledb.connect(user="myproxyuser[mysessionuser]", password="myproxyuserpw",
dsn="dbhost.example.com/orclpdb")
# PROXY_USER: MYPROXYUSER
# SESSION_USER: MYSESSIONUSER
Pooled connection examples:
# Basic Authentication without a proxy
pool = oracledb.create_pool(user="myproxyuser", password="myproxyuserpw",
dsn="dbhost.example.com/orclpdb")
connection = pool.acquire()
# PROXY_USER: None
# SESSION_USER: MYPROXYUSER
# Basic Authentication with proxy
pool = oracledb.create_pool(user="myproxyuser[mysessionuser]", password="myproxyuserpw",
dsn="dbhost.example.com/orclpdb",
homogeneous=False)
connection = pool.acquire()
# PROXY_USER: MYPROXYUSER
# SESSION_USER: MYSESSIONUSER
Note the use of a heterogeneous pool in the example above. This is required in this scenario.
4.7. Connecting Using External Authentication
Instead of storing the database username and password in Python scripts or environment variables, database access can be authenticated by an outside system. External Authentication allows applications to validate user access by an external password store (such as an Oracle Wallet), by the operating system, or with an external authentication service.
Note
Connecting to Oracle Database using external authentication is only supported in the python-oracledb Thick mode. See Enabling python-oracledb Thick mode.
4.7.1. Using an Oracle Wallet for External Authentication
The following steps give an overview of using an Oracle Wallet. Wallets should be kept securely. Wallets can be managed with Oracle Wallet Manager.
In this example the wallet is created for the myuser schema in the directory
/home/oracle/wallet_dir. The mkstore command is available from a full
Oracle client or Oracle Database installation. If you have been given wallet by
your DBA, skip to step 3.
First create a new wallet as the
oracleuser:mkstore -wrl "/home/oracle/wallet_dir" -create
This will prompt for a new password for the wallet.
Create the entry for the database user name and password that are currently hardcoded in your Python scripts. Use either of the methods shown below. They will prompt for the wallet password that was set in the first step.
Method 1 - Using an Easy Connect string:
mkstore -wrl "/home/oracle/wallet_dir" -createCredential dbhost.example.com/orclpdb myuser myuserpw
Method 2 - Using a connect name identifier:
mkstore -wrl "/home/oracle/wallet_dir" -createCredential mynetalias myuser myuserpw
The alias key
mynetaliasimmediately following the-createCredentialoption will be the connect name to be used in Python scripts. If your application connects with multiple different database users, you could create a wallet entry with different connect names for each.You can see the newly created credential with:
mkstore -wrl "/home/oracle/wallet_dir" -listCredential
Skip this step if the wallet was created using an Easy Connect String. Otherwise, add an entry in tnsnames.ora for the connect name as follows:
mynetalias = (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = dbhost.example.com)(PORT = 1521)) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = orclpdb) ) )
The file uses the description for your existing database and sets the connect name alias to
mynetalias, which is the identifier used when adding the wallet entry.Add the following wallet location entry in the sqlnet.ora file, using the
DIRECTORYyou created the wallet in:WALLET_LOCATION = (SOURCE = (METHOD = FILE) (METHOD_DATA = (DIRECTORY = /home/oracle/wallet_dir) ) ) SQLNET.WALLET_OVERRIDE = TRUE
Examine the Oracle documentation for full settings and values.
Ensure the configuration files are in a default location or TNS_ADMIN is set to the directory containing them. See Optional Oracle Net Configuration Files.
With an Oracle wallet configured, and readable by you, your scripts can connect using:
connection = oracledb.connect(externalauth=True, dsn="mynetalias")
or:
pool = oracledb.create_pool(externalauth=True, homogeneous=False,
dsn="mynetalias")
pool.acquire()
The dsn must match the one used in the wallet.
After connecting, the query:
SELECT SYS_CONTEXT('USERENV', 'SESSION_USER') FROM DUAL;
will show:
MYUSER
Note
Wallets are also used to configure Transport Layer Security (TLS) connections.
If you are using a wallet like this, you may need a database username and password
in oracledb.connect() and oracledb.create_pool() calls.
External Authentication and Proxy Authentication
The following examples show external wallet authentication combined with proxy authentication. These examples use the wallet configuration from above, with the addition of a grant to another user:
ALTER USER mysessionuser GRANT CONNECT THROUGH myuser;
After connection, you can check who the session user is with:
SELECT SYS_CONTEXT('USERENV', 'PROXY_USER'),
SYS_CONTEXT('USERENV', 'SESSION_USER')
FROM DUAL;
Standalone connection example:
# External Authentication with proxy
connection = oracledb.connect(user="[mysessionuser]", dsn="mynetalias")
# PROXY_USER: MYUSER
# SESSION_USER: MYSESSIONUSER
You can also explicitly set the externalauth parameter to True in standalone
connections as shown below. The externalauth parameter is optional.
# External Authentication with proxy when externalauth is set to True
connection = oracledb.connect(user="[mysessionuser]", dsn="mynetalias",
externalauth=True)
# PROXY_USER: MYUSER
# SESSION_USER: MYSESSIONUSER
Pooled connection example:
# External Authentication with proxy
pool = oracledb.create_pool(externalauth=True, homogeneous=False,
dsn="mynetalias")
pool.acquire(user="[mysessionuser]")
# PROXY_USER: MYUSER
# SESSION_USER: MYSESSIONUSER
The following usage is not supported:
pool = oracledb.create_pool(user="[mysessionuser]", externalauth=True,
homogeneous=False, dsn="mynetalias")
pool.acquire()
4.7.2. Operating System Authentication
With Operating System authentication, Oracle allows user authentication to be performed by the operating system. The following steps give an overview of how to implement OS Authentication on Linux.
Log in to your computer. The commands used in these steps assume the operating system user name is “oracle”.
Log in to SQL*Plus as the SYSTEM user and verify the value for the
OS_AUTHENT_PREFIXparameter:SQL> SHOW PARAMETER os_authent_prefix NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ os_authent_prefix string ops$
Create an Oracle database user using the
os_authent_prefixdetermined in step 2, and the operating system user name:
CREATE USER ops$oracle IDENTIFIED EXTERNALLY; GRANT CONNECT, RESOURCE TO ops$oracle;
In Python, connect using the following code:
connection = oracledb.connect(dsn="mynetalias")
Your session user will be OPS$ORACLE.
If your database is not on the same computer as Python, you can perform testing
by setting the database configuration parameter remote_os_authent=true.
Beware of security concerns because this is insecure.
See Oracle Database Security Guide for more information about Operating System Authentication.
4.8. Token-Based Authentication
Token-Based Authentication allows users to connect to a database by using an encrypted authentication token without having to enter a database username and password. The authentication token must be valid and not expired for the connection to be successful. Users already connected will be able to continue work after their token has expired but they will not be able to reconnect without getting a new token.
The two authentication methods supported by python-oracledb are Open Authorization (OAuth 2.0) and Oracle Cloud Infrastructure (OCI) Identity and Access Management (IAM).
4.8.1. Connecting Using OAuth 2.0 Token-Based Authentication
Oracle Cloud Infrastructure (OCI) users can be centrally managed in a Microsoft Azure Active Directory (Azure AD) service. Open Authorization (OAuth 2.0) token-based authentication allows users to authenticate to Oracle Database using Azure AD OAuth2 tokens. Currently, only Azure AD tokens are supported. Ensure that you have a Microsoft Azure account and your Oracle Database is registered with Azure AD. See Configuring the Oracle Autonomous Database for Microsoft Azure AD Integration for more information. Both Thin and Thick modes of the python-oracledb driver support OAuth 2.0 token-based authentication.
When using python-oracledb in Thick mode, Oracle Client libraries 19.15 (or later), or 21.7 (or later) are needed.
OAuth 2.0 token-based authentication can be used for both standalone connections and connection pools. Tokens can be specified using the connection parameter introduced in python-oracledb 1.1. Users of earlier python-oracledb versions can alternatively use OAuth 2.0 Token-Based Authentication Connection Strings.
4.8.1.1. OAuth2 Token Generation And Extraction
There are different ways to retrieve Azure AD OAuth2 tokens. Some of the ways to retrieve the OAuth2 tokens are detailed in Examples of Retrieving Azure AD OAuth2 Tokens. You can also retrieve Azure AD OAuth2 tokens by using Azure Identity client library for Python.
4.8.1.1.1. Example of Using a TokenHandlerOAuth Class
Here, as an example, we are using a Python script to automate the process of generating and reading the Azure AD OAuth2 tokens.
import json
import os
import oracledb
import requests
class TokenHandlerOAuth:
def __init__(self,
file_name="cached_token_file_name",
api_key="api_key",
client_id="client_id",
client_secret="client_secret"):
self.token = None
self.file_name = file_name
self.url = \
f"https://login.microsoftonline.com/{api_key}/oauth2/v2.0/token"
self.scope = \
f"https://oracledevelopment.onmicrosoft.com/{client_id}/.default"
if os.path.exists(file_name):
with open(file_name) as f:
self.token = f.read().strip()
self.api_key = api_key
self.client_id = client_id
self.client_secret = client_secret
def __call__(self, refresh):
if self.token is None or refresh:
post_data = dict(client_id=self.client_id,
grant_type="client_credentials",
scope=self.scope,
client_secret=self.client_secret)
r = requests.post(url=self.url, data=post_data)
result = json.loads(r.text)
self.token = result["access_token"]
with open(self.file_name, "w") as f:
f.write(self.token)
return self.token
The TokenHandlerOAuth class uses a callable to generate and read the OAuth2
tokens. When the callable in the TokenHandlerAuth class is invoked for the
first time to create a standalone connection or pool, the refresh parameter
is False which allows the callable to return a cached token, if desired. The
expiry date is then extracted from this token and compared with the current
date. If the token has not expired, then it will be used directly. If the token
has expired, the callable is invoked the second time with the refresh
parameter set to True.
See Example of Using a Curl Command for an alternative way to generate the tokens.
4.8.1.2. Standalone Connection Creation with OAuth2 Access Tokens
For OAuth 2.0 Token-Based Authentication, the access_token connection parameter
must be specified. This parameter should be a string (or a callable that returns a
string) specifying an Azure AD OAuth2 token.
Standalone connections can be created in the python-oracledb Thick and Thin modes
using OAuth 2.0 token-based authentication. In the examples below, the
access_token parameter is set to a callable.
In python-oracledb Thin mode
When connecting to Oracle Cloud Database with mutual TLS (mTLS) using OAuth2
tokens in the python-oracledb Thin mode, you need to explicitly set the
config_dir, wallet_location, and wallet_password parameters of
connect(). See, Connecting to Oracle Cloud Autonomous Databases.
The following example shows a standalone connection creation using OAuth 2.0 token
based authentication in the python-oracledb Thin mode. For information on
TokenHandlerOAuth() used in the example, see Example of Using a TokenHandlerOAuth Class.
connection = oracledb.connect(access_token=TokenHandlerOAuth(),
dsn=mydb_low,
config_dir="path_to_extracted_wallet_zip",
wallet_location="location_of_pem_file",
wallet_password=wp)
In python-oracledb Thick mode
In the python-oracledb Thick mode, you can create a standalone connection using OAuth2 tokens as shown in the example below. For information on TokenHandlerOAuth() used in the example, see Example of Using a TokenHandlerOAuth Class.
connection = oracledb.connect(access_token=TokenHandlerOAuth(),
externalauth=True,
dsn=mydb_low)
4.8.1.3. Connection Pool Creation with OAuth2 Access Tokens
For OAuth 2.0 Token-Based Authentication, the access_token connection
parameter must be specified. This parameter should be a string (or a callable
that returns a string) specifying an Azure AD OAuth2 token.
The externalauth parameter must be set to True in the python-oracledb Thick
mode. The homogeneous parameter must be set to True in both the
python-oracledb Thin and Thick modes.
Connection pools can be created in the python-oracledb Thick and Thin modes
using OAuth 2.0 token-based authentication. In the examples below, the
access_token parameter is set to a callable.
Note that the access_token parameter should be set to a callable. This is
useful when the connection pool needs to expand and create new connections but
the current token has expired. In such case, the callable should return a
string specifying the new, valid Azure AD OAuth2 token.
In python-oracledb Thin mode
When connecting to Oracle Cloud Database with mutual TLS (mTLS) using OAuth2
tokens in the python-oracledb Thin mode, you need to explicitly set the
config_dir, wallet_location, and wallet_password parameters of
create_pool(). See, Connecting to Oracle Cloud Autonomous Databases.
The following example shows a connection pool creation using OAuth 2.0 token
based authentication in the python-oracledb Thin mode. For information on
TokenHandlerOAuth() used in the example, see Example of Using a TokenHandlerOAuth Class.
connection = oracledb.create_pool(access_token=TokenHandlerOAuth(),
homogeneous=True, dsn=mydb_low,
config_dir="path_to_extracted_wallet_zip",
wallet_location="location_of_pem_file",
wallet_password=wp
min=1, max=5, increment=2)
In python-oracledb Thick mode
In the python-oracledb Thick mode, you can create a connection pool using OAuth2 tokens as shown in the example below. For information on TokenHandlerOAuth() used in the example, see Example of Using a TokenHandlerOAuth Class.
pool = oracledb.create_pool(access_token=TokenHandlerOAuth(),
externalauth=True, homogeneous=True,
dsn=mydb_low, min=1, max=5, increment=2)
4.8.1.4. OAuth 2.0 Token-Based Authentication Connection Strings
The connection string used by python-oracledb can specify the directory where the token file is located. This syntax is usable with older versions of python-oracledb. However, it is recommended to use connection parameters introduced in python-oracledb 1.1 instead. See OAuth 2.0 Token-Based Authentication.
Note
OAuth 2.0 Token-Based Authentication Connection Strings is only supported in the python-oracledb Thick mode. See Enabling python-oracledb Thick mode.
There are different ways to retrieve Azure AD OAuth2 tokens. Some of the ways to retrieve the OAuth2 tokens are detailed in Examples of Retrieving Azure AD OAuth2 Tokens. You can also retrieve Azure AD OAuth2 tokens by using Azure Identity client library for Python.
4.8.1.4.1. Example of Using a Curl Command
Here, as an example, we are using Curl with a Resource Owner
Password Credential (ROPC) Flow, that is, a curl command is used against
the Azure AD API to get the Azure AD OAuth2 token:
curl -X POST -H 'Content-Type: application/x-www-form-urlencoded'
https://login.microsoftonline.com/your_tenant_id/oauth2/v2.0/token
-d 'client_id=your_client_id'
-d 'grant_type=client_credentials'
-d 'scope=https://oracledevelopment.onmicrosoft.com/your_client_id/.default'
-d 'client_secret=your_client_secret'
This command generates a JSON response with token type, expiration, and access
token values. The JSON response needs to be parsed so that only the access
token is written and stored in a file. You can save the value of
access_token generated to a file and set TOKEN_LOCATION to the location
of token file. See Example of Using a TokenHandlerOAuth Class for an example of using the
TokenHandlerOAuth class to generate and read tokens.
The Oracle Net parameters TOKEN_AUTH and TOKEN_LOCATION must be set when
you are using the connection string syntax. Also, the PROTOCOL
parameter must be tcps and SSL_SERVER_DN_MATCH should be ON.
You can set TOKEN_AUTH=OAUTH. There is no default location set in this
case, so you must set TOKEN_LOCATION to either of the following:
A directory, in which case, you must create a file named
tokenwhich contains the token valueA fully qualified file name, in which case, you must specify the entire path of the file which contains the token value
You can either set TOKEN_AUTH and TOKEN_LOCATION in a sqlnet.ora file or
alternatively, you can specify it inside a connect descriptor stored in
tnsnames.ora file, for example:
db_alias =
(DESCRIPTION =
(ADDRESS=(PROTOCOL=TCPS)(PORT=1522)(HOST=xxx.oraclecloud.com))
(CONNECT_DATA=(SERVICE_NAME=xxx.adb.oraclecloud.com))
(SECURITY =
(SSL_SERVER_CERT_DN="CN=xxx.oraclecloud.com, \
O=Oracle Corporation,L=Redwood City,ST=California,C=US")
(TOKEN_AUTH=OAUTH)
(TOKEN_LOCATION="/home/user1/mytokens/oauthtoken")
)
)
The TOKEN_AUTH and TOKEN_LOCATION values in a connection string take
precedence over the sqlnet.ora settings.
Standalone connection example:
connection = oracledb.connect(dsn=db_alias, externalauth=True)
Connection pool example:
pool = oracledb.create_pool(dsn=db_alias, externalauth=True,
homogeneous=False, min=1, max=2, increment=1)
connection = pool.acquire()
4.8.2. Connecting Using OCI IAM Token-Based Authentication
Oracle Cloud Infrastructure (OCI) Identity and Access Management (IAM) provides its users with a centralized database authentication and authorization system. Using this authentication method, users can use the database access token issued by OCI IAM to authenticate to the Oracle Cloud Database. Both Thin and Thick modes of the python-oracledb driver support OCI IAM token-based authentication.
When using python-oracledb in Thick mode, Oracle Client libraries 19.14 (or later), or 21.5 (or later) are needed.
OCI IAM token-based authentication can be used for both standalone connections and connection pools. Tokens can be specified using the connection parameter introduced in python-oracledb 1.1. Users of earlier python-oracledb versions can alternatively use OCI IAM Token-Based Authentication Connection Strings.
4.8.2.1. OCI IAM Token Generation and Extraction
Authentication tokens can be generated through execution of an Oracle Cloud Infrastructure command line interface (OCI-CLI) command
oci iam db-token get
On Linux, a folder .oci/db-token will be created in your home directory.
It will contain the token and private key files needed by python-oracledb.
4.8.2.1.1. Example of Using a TokenHandlerIAM Class
Here, as an example, we are using a Python script to automate the process of generating and reading the OCI IAM tokens.
import os
import oracledb
class TokenHandlerIAM:
def __init__(self,
dir_name="dir_name",
command="oci iam db-token get"):
self.dir_name = dir_name
self.command = command
self.token = None
self.private_key = None
def __call__(self, refresh):
if refresh:
if os.system(self.command) != 0:
raise Exception("token command failed!")
if self.token is None or refresh:
self.read_token_info()
return (self.token, self.private_key)
def read_token_info(self):
token_file_name = os.path.join(self.dir_name, "token")
pkey_file_name = os.path.join(self.dir_name, "oci_db_key.pem")
with open(token_file_name) as f:
self.token = f.read().strip()
with open(pkey_file_name) as f:
if oracledb.is_thin_mode():
self.private_key = f.read().strip()
else:
lines = [s for s in f.read().strip().split("\n")
if s not in ('-----BEGIN PRIVATE KEY-----',
'-----END PRIVATE KEY-----')]
self.private_key = "".join(lines)
The TokenHandlerIAM class uses a callable to generate and read the OCI IAM
tokens. When the callable in the TokenHandlerIAM class is invoked for the first
time to create a standalone connection or pool, the refresh parameter is
False which allows the callable to return a cached token, if desired. The
expiry date is then extracted from this token and compared with the current
date. If the token has not expired, then it will be used directly. If the token
has expired, the callable is invoked the second time with the refresh
parameter set to True.
4.8.2.2. Standalone Connection Creation with OCI IAM Access Tokens
For OCI IAM Token-Based Authentication, the access_token connection parameter
must be specified. This parameter should be a 2-tuple (or a callable that returns
a 2-tuple) containing the token and private key.
Standalone connections can be created in the python-oracledb Thick and Thin modes
using OCI IAM token-based authentication. In the examples below, the
access_token parameter is set to a callable.
In python-oracledb Thin mode
When connecting to Oracle Cloud Database with mutual TLS (mTLS) using OCI IAM
tokens in the python-oracledb Thin mode, you need to explicitly set the
config_dir, wallet_location, and wallet_password parameters of
connect(). See, Connecting to Oracle Cloud Autonomous Databases.
The following example shows a standalone connection creation using OCI IAM token
based authentication in the python-oracledb Thin mode. For information on
TokenHandlerIAM() used in the example, see Example of Using a TokenHandlerIAM Class.
connection = oracledb.connect(access_token=TokenHandlerIAM(),
dsn=mydb_low,
config_dir="path_to_extracted_wallet_zip",
wallet_location="location_of_pem_file",
wallet_password=wp)
In python-oracledb Thick mode
In the python-oracledb Thick mode, you can create a standalone connection using OCI IAM tokens as shown in the example below. For information on TokenHandlerIAM() used in the example, see Example of Using a TokenHandlerIAM Class.
connection = oracledb.connect(access_token=TokenHandlerIAM(),
externalauth=True,
dsn=mydb_low)
4.8.2.3. Connection Pool Creation with OCI IAM Access Tokens
For OCI IAM Token-Based Authentication, the access_token connection
parameter must be specified. This parameter should be a 2-tuple (or a callable
that returns a 2-tuple) containing the token and private key.
The externalauth parameter must be set to True in the python-oracledb Thick
mode. The homogeneous parameter must be set to True in both the
python-oracledb Thin and Thick modes.
Connection pools can be created in the python-oracledb Thick and Thin modes
using OCI IAM token-based authentication. In the examples below, the
access_token parameter is set to a callable.
Note that the access_token parameter should be set to a callable. This is
useful when the connection pool needs to expand and create new connections but
the current token has expired. In such case, the callable should return a
2-tuple (token, private key) specifying the new, valid access token.
In python-oracledb Thin mode
When connecting to Oracle Cloud Database with mutual TLS (mTLS) using OCI IAM
tokens in the python-oracledb Thin mode, you need to explicitly set the
config_dir, wallet_location, and wallet_password parameters of
create_pool(). See, Connecting to Oracle Cloud Autonomous Databases.
The following example shows a connection pool creation using OCI IAM token
based authentication in the python-oracledb Thin mode. For information on
TokenHandlerIAM() used in the example, see Example of Using a TokenHandlerIAM Class.
connection = oracledb.connect(access_token=TokenHandlerIAM(),
homogeneous=True, dsn=mydb_low,
config_dir="path_to_extracted_wallet_zip",
wallet_location="location_of_pem_file",
wallet_password=wp
min=1, max=5, increment=2)
In python-oracledb Thick mode
In the python-oracledb Thick mode, you can create a connection pool using OCI IAM tokens as shown in the example below. For information on TokenHandlerIAM() used in the example, see Example of Using a TokenHandlerIAM Class.
pool = oracledb.create_pool(access_token=TokenHandlerIAM(),
externalauth=True,
homogeneous=True,
dsn=mydb_low,
min=1, max=5, increment=2)
4.8.2.4. OCI IAM Token-Based Authentication Connection Strings
The connection string used by python-oracledb can specify the directory where the token and private key files are located. This syntax is usable with older versions of python-oracledb. However, it is recommended to use connection parameters introduced in python-oracledb 1.1 instead. See OCI IAM Token-Based Authentication.
Note
OCI IAM Token-Based Authentication Connection Strings is only supported in the python-oracledb Thick mode. See Enabling python-oracledb Thick mode.
The Oracle Cloud Infrastructure command line interface (OCI-CLI) can be used
externally to get tokens and private keys from OCI IAM, for example with the
OCI-CLI oci iam db-token get command.
The Oracle Net parameter TOKEN_AUTH must be set when you are using the
connection string syntax. Also, the PROTOCOL parameter must be tcps
and SSL_SERVER_DN_MATCH should be ON.
You can set TOKEN_AUTH=OCI_TOKEN in a sqlnet.ora file.
Alternatively, you can specify it in a connect descriptor, for example:
db_alias =
(DESCRIPTION =
(ADDRESS=(PROTOCOL=TCPS)(PORT=1522)(HOST=xxx.oraclecloud.com))
(CONNECT_DATA=(SERVICE_NAME=xxx.adb.oraclecloud.com))
(SECURITY =
(SSL_SERVER_CERT_DN="CN=xxx.oraclecloud.com, \
O=Oracle Corporation,L=Redwood City,ST=California,C=US")
(TOKEN_AUTH=OCI_TOKEN)
)
)
The default location for the token and private key is the same default location
that the OCI-CLI tool writes to. For example ~/.oci/db-token/ on Linux.
If the token and private key files are not in the default location then their
directory must be specified with the TOKEN_LOCATION parameter in a
sqlnet.ora file or in a connect descriptor stored inside
tnsnames.ora file, for example:
db_alias =
(DESCRIPTION =
(ADDRESS=(PROTOCOL=TCPS)(PORT=1522)(HOST=xxx.oraclecloud.com))
(CONNECT_DATA=(SERVICE_NAME=xxx.adb.oraclecloud.com))
(SECURITY =
(SSL_SERVER_CERT_DN="CN=xxx.oraclecloud.com, \
O=Oracle Corporation,L=Redwood City,ST=California,C=US")
(TOKEN_AUTH=OCI_TOKEN)
(TOKEN_LOCATION="/path/to/token/folder")
)
)
The TOKEN_AUTH and TOKEN_LOCATION values in a connection string take
precedence over the sqlnet.ora settings.
Standalone connection example:
connection = oracledb.connect(dsn=db_alias, externalauth=True)
Connection pool example:
pool = oracledb.create_pool(dsn=db_alias, externalauth=True,
homogeneous=False, min=1, max=2, increment=1)
connection = pool.acquire()
4.9. Privileged Connections
The mode parameter of the function oracledb.connect() specifies
the database privilege that you want to associate with the user.
The example below shows how to connect to Oracle Database as SYSDBA:
connection = oracledb.connect(user="sys", password=syspwd,
dsn="dbhost.example.com/orclpdb",
mode=oracledb.AUTH_MODE_SYSDBA)
with connection.cursor() as cursor:
cursor.execute("GRANT SYSOPER TO hr")
This is equivalent to executing the following in SQL*Plus:
CONNECT sys/syspwd@dbhost.example.com/orclpdb AS SYSDBA
GRANT SYSOPER TO hr;
In python-oracledb Thick mode, when python-oracledb uses Oracle Client
libraries from a database software installation, you can use “bequeath”
connections to databases that are also using the same libraries. Do this by
setting the standard Oracle environment variables such as ORACLE_HOME and
ORACLE_SID and connecting in Python like:
oracledb.init_oracle_client()
conn = oracledb.connect(mode=oracledb.SYSDBA)
This is equivalent to executing the following in SQL*Plus:
CONNECT / AS SYSDBA
4.10. Securely Encrypting Network Traffic to Oracle Database
You can encrypt data transferred between the Oracle Database and python-oracledb so that unauthorized parties are not able to view plain text values as the data passes over the network.
Both python-oracledb Thin and Thick modes support TLS. Refer to the Oracle Database Security Guide for more configuration information.
4.10.1. Native Network Encryption
The python-oracledb Thick mode can additionally use Oracle Database’s native network encryption.
With native network encryption, the client and database server negotiate a key using Diffie-Hellman key exchange. This provides protection against man-in-the-middle attacks.
Native network encryption can be configured by editing Oracle Net’s optional sqlnet.ora configuration file. The file on either the database server and/or on each python-oracledb ‘client’ machine can be configured. Parameters control whether data integrity checking and encryption is required or just allowed, and which algorithms the client and server should consider for use.
As an example, to ensure all connections to the database are checked for
integrity and are also encrypted, create or edit the Oracle Database
$ORACLE_HOME/network/admin/sqlnet.ora file. Set the checksum negotiation
to always validate a checksum and set the checksum type to your desired value.
The network encryption settings can similarly be set. For example, to use the
SHA512 checksum and AES256 encryption use:
SQLNET.CRYPTO_CHECKSUM_SERVER = required
SQLNET.CRYPTO_CHECKSUM_TYPES_SERVER = (SHA512)
SQLNET.ENCRYPTION_SERVER = required
SQLNET.ENCRYPTION_TYPES_SERVER = (AES256)
If you definitely know that the database server enforces integrity and
encryption, then you do not need to configure python-oracledb separately. However,
you can also, or alternatively do so, depending on your business needs. Create
a sqlnet.ora on your client machine and locate it with other
Optional Oracle Net Configuration Files:
SQLNET.CRYPTO_CHECKSUM_CLIENT = required
SQLNET.CRYPTO_CHECKSUM_TYPES_CLIENT = (SHA512)
SQLNET.ENCRYPTION_CLIENT = required
SQLNET.ENCRYPTION_TYPES_CLIENT = (AES256)
The client and server sides can negotiate the protocols used if the settings indicate more than one value is accepted.
Note that these are example settings only. You must review your security requirements and read the documentation for your Oracle version. In particular, review the available algorithms for security and performance.
The NETWORK_SERVICE_BANNER column of the database view
V$SESSION_CONNECT_INFO can be used to verify the
encryption status of a connection. For example with SQL*Plus:
SQL> SELECT network_service_banner FROM v$session_connect_info;
If the connection is encrypted, then this query prints an output that includes the available encryption service, the crypto-checksumming service, and the algorithms in use, such as:
NETWORK_SERVICE_BANNER
-------------------------------------------------------------------------------------
TCP/IP NT Protocol Adapter for Linux: Version 19.0.0.0.0 - Production
Encryption service for Linux: Version 19.0.1.0.0 - Production
AES256 Encryption service adapter for Linux: Version 19.0.1.0.0 - Production
Crypto-checksumming service for Linux: Version 19.0.1.0.0 - Production
SHA256 Crypto-checksumming service adapter for Linux: Version 19.0.1.0.0 - Production
If the connection is unencrypted, then the query will only print the available encryption and crypto-checksumming services in the output. For example:
NETWORK_SERVICE_BANNER
-------------------------------------------------------------------------------------
TCP/IP NT Protocol Adapter for Linux: Version 19.0.0.0.0 - Production
Encryption service for Linux: Version 19.0.1.0.0 - Production
Crypto-checksumming service for Linux: Version 19.0.1.0.0 - Production
For more information about Oracle Data Network Encryption and Integrity, and for information about configuring TLS network encryption, refer to the Oracle Database Security Guide.
4.11. Resetting Passwords
After connecting to Oracle Database, passwords can be changed by calling
Connection.changepassword():
# Get the passwords from somewhere, such as prompting the user
oldpwd = getpass.getpass(f"Old Password for {username}: ")
newpwd = getpass.getpass(f"New Password for {username}: ")
connection.changepassword(oldpwd, newpwd)
When a password has expired and you cannot connect directly, you can connect
and change the password in one operation by using the newpassword parameter
of the function oracledb.connect() constructor:
# Get the passwords from somewhere, such as prompting the user
oldpwd = getpass.getpass(f"Old Password for {username}: ")
newpwd = getpass.getpass(f"New Password for {username}: ")
connection = oracledb.connect(user=username, password=oldpwd,
dsn="dbhost.example.com/orclpdb",
newpassword=newpwd)
4.12. Connecting to Oracle Cloud Autonomous Databases
Python applications can connect to Oracle Autonomous Database (ADB) in Oracle Cloud using one-way TLS (Transport Layer Security) or mutual TLS (mTLS). One-way TLS and mTLS provide enhanced security for authentication and encryption.
A database username and password are still required for your application connections. If you need to create a new database schema so you do not login as the privileged ADMIN user, refer to the relevant Oracle Cloud documentation, for example see Create Database Users in the Oracle Autonomous Database manual.
4.12.1. One-way TLS Connection to Oracle Autonomous Database
With one-way TLS, python-oracledb applications can connect to Oracle ADB without using a wallet. Both Thin and Thick modes of the python-oracledb driver support one-way TLS. Applications that use the python-oracledb Thick mode, can connect to the Oracle ADB through one-way TLS only when using Oracle Client library versions 19.14 (or later) or 21.5 (or later).
To enable one-way TLS for an ADB instance, complete the following steps in an Oracle Cloud console in the Autonomous Database Information section of the ADB instance details:
Click the Edit link next to Access Control List to update the Access Control List (ACL). The Edit Access Control List dialog box is displayed.
In the Edit Access Control List dialog box, select the type of address list entries and the corresponding values. You can include the required IP addresses, hostnames, or Virtual Cloud Networks (VCNs). The ACL limits access to only the IP addresses or VCNs that have been defined and blocks all other incoming traffic.
Navigate back to the ADB instance details page and click the Edit link next to Mutual TLS (mTLS) Authentication. The Edit Mutual TLS Authentication is displayed.
In the Edit Mutual TLS Authentication dialog box, deselect the Require mutual TLS (mTLS) authentication check box to disable the mTLS requirement on Oracle ADB and click Save Changes.
Navigate back to the ADB instance details page and click DB Connection on the top of the page. A Database Connection dialog box is displayed.
In the Database Connection dialog box, select TLS from the Connection Strings drop-down list.
Copy the appropriate Connection String of the database instance used by your application.
Applications can connect to your Oracle ADB instance using the database credentials and the copied connect descriptor. For example, to connect as the ADMIN user:
cs = '''(description = (retry_count=20)(retry_delay=3)(address=(protocol=tcps)
(port=1522)(host=xxx.oraclecloud.com))(connect_data=(service_name=xxx.adb.oraclecloud.com))
(security=(ssl_server_dn_match=yes)(ssl_server_cert_dn="CN=xxx.oraclecloud.com,
O=Oracle Corporation, L=Redwood City, T=California, C=US")))'''
connection = oracledb.connect(user="admin", password=pw, dsn=cs)
You can download the ADB connection wallet using the DB Connection button
and extract the tnsnames.ora file, or create one yourself if you prefer to
keep connections strings out of application code, see Net Service Names for Connection Strings.
You may be interested in the blog post Easy wallet-less connections to Oracle Autonomous Databases in Python.
4.12.2. Mutual TLS (mTLS) Connection to Oracle Autonomous Database
To enable python-oracledb connections to Oracle Autonomous Database in Oracle Cloud using mTLS, a wallet needs to be downloaded from the cloud console. mTLS is sometimes called Two-way TLS.
4.12.2.1. Install the Wallet and Network Configuration Files
From the Oracle Cloud console for the database, download the wallet zip file using the DB Connection button. The zip contains the wallet and network configuration files. When downloading the zip, the cloud console will ask you to create a wallet password. This password is used by python-oracledb in Thin mode, but not in Thick mode.
Note: keep wallet files in a secure location and only share them and the password with authorized users.
In python-oracledb Thin mode
For python-oracledb in Thin mode, only two files from the zip are needed:
tnsnames.ora- Maps net service names used for application connection strings to your database servicesewallet.pem- Enables SSL/TLS connections in Thin mode. Keep this file secure
If you do not have a PEM file, see Creating a PEM File for python-oracledb Thin Mode.
Unzip the wallet zip file and move the required files to a location such as
/opt/OracleCloud/MYDB.
Connection can be made using your database credentials and setting the dsn
parameter to the desired network alias from the tnsnames.ora file. The
config_dir parameter indicates the directory containing tnsnames.ora.
The wallet_location parameter is the directory containing the PEM file. In
this example the files are in the same directory. The wallet_password
parameter should be set to the password created in the cloud console when
downloading the wallet. For example, to connect as the ADMIN user using the
mydb_low network service name:
connection = oracledb.connect(user="admin", password=pw, dsn="mydb_low",
config_dir="/opt/OracleCloud/MYDB",
wallet_location="/opt/OracleCloud/MYDB",
wallet_password=wp)
In python-oracledb Thick mode
For python-oracledb in Thick mode, only these files from the zip are needed:
tnsnames.ora- Maps net service names used for application connection strings to your database servicessqlnet.ora- Configures Oracle Network settingscwallet.sso- Enables SSL/TLS connections in Thick mode. Keep this file secure
Unzip the wallet zip file. There are two options for placing the required files:
Move the three files to the
network/admindirectory of the client libraries used by your application. For example if you are using Instant Client 19c and it is in$HOME/instantclient_19_15, then you would put the wallet files in$HOME/instantclient_19_15/network/admin/.Connection can be made using your database credentials and setting the
dsnparameter to the desired network alias from thetnsnames.orafile. For example, to connect as the ADMIN user using themydb_lownetwork service name:connection = oracledb.connect(user="admin", password=pw, dsn="mydb_low")
Alternatively, move the three files to any accessible directory, for example
/opt/OracleCloud/MYDB.Then edit
sqlnet.oraand change the wallet location directory to the directory containing thecwallet.ssofile. For example:WALLET_LOCATION = (SOURCE = (METHOD = file) (METHOD_DATA = (DIRECTORY="/opt/OracleCloud/MYDB"))) SSL_SERVER_DN_MATCH=yes
Since the
tnsnames.oraandsqlnet.orafiles are not in the default location, your application needs to indicate where they are, either with theconfig_dirparameter tooracledb.init_oracle_client(), or using theTNS_ADMINenvironment variable. See Optional Oracle Net Configuration Files. (Neither of these settings are needed, and you do not need to editsqlnet.ora, if you have put all the files in thenetwork/admindirectory.)For example, to connect as the ADMIN user using the
mydb_lownetwork service name:oracledb.init_oracle_client(config_dir="/opt/OracleCloud/MYDB") connection = oracledb.connect(user="admin", password=pw, dsn="mydb_low")
In python-oracle Thick mode, to create mTLS connections in one Python process
to two or more Oracle Autonomous Databases, move each cwallet.sso file to
its own directory. For each connection use different connection string
WALLET_LOCATION parameters to specify the directory of each cwallet.sso
file. It is recommended to use Oracle Client libraries 19.17 (or later) when
using multiple wallets.
4.12.2.2. Access Through a Proxy
If you are behind a firewall, you can tunnel TLS/SSL connections via a proxy using HTTPS_PROXY in the connect descriptor or setting connection attributes. Successful connection depends on specific proxy configurations. Oracle does not recommend doing this when performance is critical.
In python-oracledb Thin mode
The proxy settings can be passed during connection creation:
connection = oracledb.connect(user="admin", password=pw, dsn="mydb_low",
config_dir="/opt/OracleCloud/MYDB",
wallet_location="/opt/OracleCloud/MYDB", wallet_password=wp,
https_proxy='myproxy.example.com', https_proxy_port=80)
Alternatively, edit tnsnames.ora and add an HTTPS_PROXY proxy name and
HTTPS_PROXY_PORT port to the connect descriptor address list of any service
name you plan to use, for example:
mydb_low = (description=
(address=
(https_proxy=myproxy.example.com)(https_proxy_port=80)
(protocol=tcps)(port=1522)(host= . . . )
connection = oracledb.connect(user="admin", password=pw, dsn="mydb_low",
config_dir="/opt/OracleCloud/MYDB",
wallet_location="/opt/OracleCloud/MYDB", wallet_password=wp)
In python-oracledb Thick mode
Edit sqlnet.ora and add a line:
SQLNET.USE_HTTPS_PROXY=on
Edit tnsnames.ora and add an HTTPS_PROXY proxy name and
HTTPS_PROXY_PORT port to the connect descriptor address list of any service
name you plan to use, for example:
mydb_high = (description=
(address=
(https_proxy=myproxy.example.com)(https_proxy_port=80)
(protocol=tcps)(port=1522)(host= . . . )
4.12.2.3. Using the Easy Connect Syntax with Autonomous Database
When python-oracledb is using Oracle Client libraries 19c or later, you can optionally use the Easy Connect syntax to connect to Oracle Autonomous Database.
The mapping from the cloud tnsnames.ora entries to an Easy Connect Plus
string is:
protocol://host:port/service_name?wallet_location=/my/dir&retry_count=N&retry_delay=N
For example, if your tnsnames.ora file had an entry:
cjjson_high = (description=(retry_count=20)(retry_delay=3)
(address=(protocol=tcps)(port=1522)
(host=xxx.oraclecloud.com))
(connect_data=(service_name=abc_cjjson_high.adb.oraclecloud.com))
(security=(ssl_server_cert_dn="CN=xxx.oraclecloud.com,O=Oracle Corporation,L=Redwood City,ST=California,C=US")))
Then your applications can connect using the connection string:
dsn = "tcps://xxx.oraclecloud.com:1522/abc_cjjson_high.adb.oraclecloud.com?wallet_location=/Users/cjones/Cloud/CJJSON&retry_count=20&retry_delay=3"
connection = oracledb.connect(user="hr", password=userpwd, dsn=dsn)
The wallet_location parameter needs to be set to the directory containing
the cwallet.sso or ewallet.pem file from the wallet zip. The other
wallet files, including tnsnames.ora, are not needed when you use the Easy
Connect Plus syntax.
You can add other Easy Connect parameters to the connection string, for example:
dsn = dsn + "&https_proxy=myproxy.example.com&https_proxy_port=80"
With python-oracledb Thin mode, the wallet password needs to be passed as a connection parameter.
4.12.2.4. Creating a PEM File for python-oracledb Thin Mode
For mutual TLS in python-oracledb Thin mode, the certificate must be Privacy
Enhanced Mail (PEM) format. If you are using Oracle Autonomous Database and
your wallet zip file does not already include a PEM file, then you can convert
the PKCS12 ewallet.p12 file to PEM format using third party tools or the
script below.
For example, invoke the conversion script by passing the wallet password and the directory containing the PKCS file:
python create_pem.py --wallet-password 'xxxxx' /Users/scott/cloud_configs/MYDBDIR
Once the PEM file has been created, you can use it by passing its directory
location as the wallet_location parameter to oracledb.connect() or
oracledb.create_pool(). These methods also accept a
wallet_password parameter. See Mutual TLS (mTLS) Connection to Oracle Autonomous Database.
Script to convert from PKCS12 to PEM
# create_pem.py
import argparse
import getpass
import os
from cryptography.hazmat.primitives.serialization \
import pkcs12, Encoding, PrivateFormat, BestAvailableEncryption, \
NoEncryption
# parse command line
parser = argparse.ArgumentParser(description="convert PKCS#12 to PEM")
parser.add_argument("wallet_location",
help="the directory in which the PKCS#12 encoded "
"wallet file ewallet.p12 is found")
parser.add_argument("--wallet-password",
help="the password for the wallet which is used to "
"decrypt the PKCS#12 encoded wallet file; if not "
"specified, it will be requested securely")
parser.add_argument("--no-encrypt",
dest="encrypt", action="store_false", default=True,
help="do not encrypt the converted PEM file with the "
"wallet password")
args = parser.parse_args()
# validate arguments and acquire password if one was not specified
pkcs12_file_name = os.path.join(args.wallet_location, "ewallet.p12")
if not os.path.exists(pkcs12_file_name):
msg = f"wallet location {args.wallet_location} does not contain " \
"ewallet.p12"
raise Exception(msg)
if args.wallet_password is None:
args.wallet_password = getpass.getpass()
pem_file_name = os.path.join(args.wallet_location, "ewallet.pem")
pkcs12_data = open(pkcs12_file_name, "rb").read()
result = pkcs12.load_key_and_certificates(pkcs12_data,
args.wallet_password.encode())
private_key, certificate, additional_certificates = result
if args.encrypt:
encryptor = BestAvailableEncryption(args.wallet_password.encode())
else:
encryptor = NoEncryption()
with open(pem_file_name, "wb") as f:
f.write(private_key.private_bytes(Encoding.PEM, PrivateFormat.PKCS8,
encryptor))
f.write(certificate.public_bytes(Encoding.PEM))
for cert in additional_certificates:
f.write(cert.public_bytes(Encoding.PEM))
print("PEM file", pem_file_name, "written.")
4.13. Connecting using Multiple Wallets
You can make multiple connections with different wallets in one Python process.
In python-oracledb Thin mode
To use multiple wallets in python-oracledb Thin mode, pass the different
connection strings, wallet locations, and wallet password (if required) in each
oracledb.connect() call or when creating a connection pool:
connection = oracledb.connect(user=user_name, password=userpw, dsn=dsn,
config_dir="path_to_extracted_wallet_zip",
wallet_location="location_of_pem_file",
wallet_password=walletpw)
The config_dir parameter is the directory containing the tnsnames.ora file. The wallet_location parameter is the directory
containing the ewallet.pem file. If you are using Oracle Autonomous
Database, both of these paths are typically the same directory where the
wallet.zip file was extracted. The dsn should specify a TCPS
connection.
In python-oracledb Thick mode
To use multiple wallets in python-oracledb Thick mode, a TCPS connection string
containing the MY_WALLET_DIRECTORY option needs to be created:
dsn = "mydb_high" # one of the network aliases from tnsnames.ora
params = oracledb.ConnectParams(config_dir="path_to_extracted_wallet_zip",
wallet_location="path_location_of_sso_file")
params.parse_connect_string(dsn)
dsn = params.get_connect_string()
connection = oracledb.connect(user=user_name, password=password, dsn=dsn)
The config_dir parameter should be the directory containing the
tnsnames.ora and sqlnet.ora files. The
wallet_location parameter is the directory containing the cwallet.sso
file. If you are using Oracle Autonomous Database, both of these paths are
typically the same directory where the wallet.zip file was extracted.
Note
Use Oracle Client libraries 19.17, or later, or use Oracle Client 21c. They contain important bug fixes for using multiple wallets in the one process.
4.14. Connecting to Sharded Databases
Oracle Sharding can be used to horizontally partition data across independent databases. A database table can be split so each shard contains a table with the same columns but a different subset of rows. These tables are known as sharded tables. Sharding is configured in Oracle Database, see the Oracle Sharding manual. Sharding requires Oracle Database and Oracle Client libraries 12.2, or later.
Note
Sharding is only supported in the python-oracledb Thick mode. See Enabling python-oracledb Thick mode.
The oracledb.connect() and ConnectionPool.acquire() functions
accept shardingkey and supershardingkey parameters that are a sequence
of values used to route the connection directly to a given shard. A sharding
key is always required. A super sharding key is additionally required when
using composite sharding, which is when data has been partitioned by a list or
range (the super sharding key), and then further partitioned by a sharding key.
When creating a connection pool, the oracledb.create_pool() attribute
max_sessions_per_shard can be set. This is used to balance connections in
the pool equally across shards. It requires Oracle Client libraries 18.3 or
later.
Shard key values may be of type string (mapping to VARCHAR2 shard keys), number (NUMBER), bytes (RAW), or date (DATE). Multiple types may be used in each array. Sharding keys of TIMESTAMP type are not supported.
When connected to a shard, queries will only return data from that shard. For queries that need to access data from multiple shards, connections can be established to the coordinator shard catalog database. In this case, no shard key or super shard key is used.
As an example of direct connection, if sharding had been configured on a single VARCHAR2 column like:
CREATE SHARDED TABLE customers (
cust_id NUMBER,
cust_name VARCHAR2(30),
class VARCHAR2(10) NOT NULL,
signup_date DATE,
cust_code RAW(20),
CONSTRAINT cust_name_pk PRIMARY KEY(cust_name))
PARTITION BY CONSISTENT HASH (cust_name)
PARTITIONS AUTO TABLESPACE SET ts1;
then direct connection to a shard can be made by passing a single sharding key:
connection = oracledb.connect(user="hr", password=userpwd,
dsn="dbhost.example.com/orclpdb",
shardingkey=["SCOTT"])
Numbers keys can be used in a similar way:
connection = oracledb.connect(user="hr", password=userpwd,
dsn="dbhost.example.com/orclpdb",
shardingkey=[110])
When sharding by DATE, you can connect like:
import datetime
d = datetime.datetime(2014, 7, 3)
connection = oracledb.connect(user="hr", password=userpwd,
dsn="dbhost.example.com/orclpdb",
shardingkey=[d])
When sharding by RAW, you can connect like:
b = b'\x01\x04\x08';
connection = oracledb.connect(user="hr", password=userpwd,
dsn="dbhost.example.com/orclpdb",
shardingkey=[b])
Multiple keys can be specified, for example:
key_list = [70, "SCOTT", "gold", b'\x00\x01\x02']
connection = oracledb.connect(user="hr", password=userpwd,
dsn="dbhost.example.com/orclpdb",
shardingkey=key_list)
A super sharding key example is:
connection = oracledb.connect(user="hr", password=userpwd,
dsn="dbhost.example.com/orclpdb",
supershardingkey=["goldclass"],
shardingkey=["SCOTT"])