3. API: Connection Objects

A Connection object can be created with oracledb.connect() or with ConnectionPool.acquire().

Note

Any outstanding database transaction will be rolled back when the connection object is destroyed or closed. You must perform a commit first if you want data to persist in the database, see Managing Transactions.

3.1. Connection Methods

Connection.__enter__(): The entry point for the connection as a context manager. It returns itself.

Note

This method is an extension to the DB API definition.

Connection.__exit__(): The exit point for the connection as a context manager. This will close the connection and roll back any uncommitted transaction.

Note

This method is an extension to the DB API definition.

Connection.begin([formatId, transactionId, branchId])

Explicitly begins a new transaction. Without parameters, this explicitly begins a local transaction; otherwise, this explicitly begins a distributed (global) transaction with the given parameters. See the Oracle documentation for more details.

Note that in order to make use of global (distributed) transactions, the internal_name and external_name attributes must be set.

Deprecated since 1.0.

Use the method Connection.tpc_begin() instead.

Note

This method is an extension to the DB API definition.

Connection.cancel(): Breaks a long-running statement.

Note

This method is an extension to the DB API definition.

Connection.changepassword(oldpassword, newpassword): Changes the password for the user to which the connection is connected.

Note

This method is an extension to the DB API definition.

Connection.close()

Closes the connection now and makes it unusable for further operations. An Error exception will be raised if any operation is attempted with this connection after this method is completed successfully.

All open cursors and LOBs created by the connection will be closed and will also no longer be usable.

Internally, references to the connection are held by cursor objects, LOB objects, subscription objects, etc. Once all of these references are released, the connection itself will be closed automatically. Either control references to these related objects carefully or explicitly close connections in order to ensure sufficient resources are available.

Connection.commit(): Commits any pending transactions to the database.

Connection.createlob(lob_type, data=None)

Creates and returns a new temporary LOB object of the specified type. The lob_type parameter should be one of oracledb.DB_TYPE_CLOB, oracledb.DB_TYPE_BLOB, or oracledb.DB_TYPE_NCLOB.

If data is supplied, it will be written to the temporary LOB before it is returned.

Changed in version 2.0: The parameter data was added.

Note

This method is an extension to the DB API definition.

Connection.cursor(): Returns a new cursor object using the connection.

Connection.decode_oson(data): Decodes OSON-encoded bytes and returns the object encoded in those bytes. This is useful for fetching columns which have the check constraint IS JSON FORMAT OSON enabled.

New in version 2.1.0.

Connection.encode_oson(value): Encodes a Python value into OSON-encoded bytes and returns them. This is useful for inserting into columns which have the check constraint IS JSON FORMAT OSON enabled.

New in version 2.1.0.

Connection.getSodaDatabase(): Returns a SodaDatabase object for Simple Oracle Document Access (SODA). All SODA operations are performed either on the returned SodaDatabase object or from objects created by the returned SodaDatabase object. See here for additional information on SODA.

Note

This method is an extension to the DB API definition.

Connection.gettype(name): Returns a type object given its name. This can then be used to create objects which can be bound to cursors created by this connection.

Note

This method is an extension to the DB API definition.

Connection.is_healthy()

This function returns a boolean indicating the health status of a connection.

Connections may become unusable in several cases, such as, if the network socket is broken, if an Oracle error indicates the connection is unusable, or, after receiving a planned down notification from the database.

This function is best used before starting a new database request on an existing standalone connection. Pooled connections internally perform this check before returning a connection to the application.

If this function returns False, the connection should be not be used by the application and a new connection should be established instead.

This function performs a local check. To fully check a connection’s health, use Connection.ping() which performs a round-trip to the database.

Connection.msgproperties(payload, correlation, delay, exceptionq, expiration, priority)

Returns an object specifying the properties of messages used in advanced queuing. See Message Properties for more information.

Each of the parameters are optional. If specified, they act as a shortcut for setting each of the equivalently named properties.

Note

This method is an extension to the DB API definition.

Connection.ping(): Pings the database to verify if the connection is valid.

Note

This method is an extension to the DB API definition.

Connection.prepare()

Prepares the distributed (global) transaction for commit. Return a boolean indicating if a transaction was actually prepared in order to avoid the error ORA-24756 (transaction does not exist).

Deprecated since python-oracledb 1.0.

Use the method Connection.tpc_prepare() instead.

Note

This method is an extension to the DB API definition.

Connection.queue(name, payload_type=None)

Creates a queue which is used to enqueue and dequeue messages in Advanced Queuing.

The name parameter is expected to be a string identifying the queue in which messages are to be enqueued or dequeued.

The payload_type parameter, if specified, is expected to be an object type that identifies the type of payload the queue expects. If the string “JSON” is specified, JSON data is enqueued and dequeued. If not specified, RAW data is enqueued and dequeued.

For consistency and compliance with the PEP 8 naming style, the parameter payloadType was renamed to payload_type. The old name will continue to work as a keyword parameter for a period of time.

Note

This method is an extension to the DB API definition.

Connection.rollback(): Rolls back any pending transactions.

Connection.shutdown([mode])

Shuts down the database. In order to do this the connection must be connected as SYSDBA or SYSOPER. Two calls must be made unless the mode specified is DBSHUTDOWN_ABORT. An example is shown below:

import oracledb

connection = oracledb.connect(mode = oracledb.SYSDBA)
connection.shutdown(mode = oracledb.DBSHUTDOWN_IMMEDIATE)
cursor = connection.cursor()
cursor.execute("alter database close normal")
cursor.execute("alter database dismount")
connection.shutdown(mode = oracledb.DBSHUTDOWN_FINAL)

Note

This method is an extension to the DB API definition.

Connection.startup(force=False, restrict=False, pfile=None)

Starts up the database. This is equivalent to the SQL*Plus command “startup nomount”. The connection must be connected as SYSDBA or SYSOPER with the PRELIM_AUTH option specified for this to work.

The pfile parameter, if specified, is expected to be a string identifying the location of the parameter file (PFILE) which will be used instead of the stored parameter file (SPFILE).

An example is shown below:

import oracledb

connection = oracledb.connect(
        mode=oracledb.SYSDBA | oracledb.PRELIM_AUTH)
connection.startup()
connection = oracledb.connect(mode=oracledb.SYSDBA)
cursor = connection.cursor()
cursor.execute("alter database mount")
cursor.execute("alter database open")

Note

This method is an extension to the DB API definition.

Connection.subscribe(namespace=oracledb.SUBSCR_NAMESPACE_DBCHANGE, protocol=oracledb.SUBSCR_PROTO_OCI, callback=None, timeout=0, operations=OPCODE_ALLOPS, port=0, qos=0, ip_address=None, grouping_class=0, grouping_value=0, grouping_type=oracledb.SUBSCR_GROUPING_TYPE_SUMMARY, name=None, client_initiated=False)

Returns a new subscription object that receives notifications for events that take place in the database that match the given parameters.

The namespace parameter specifies the namespace the subscription uses. It can be one of oracledb.SUBSCR_NAMESPACE_DBCHANGE or oracledb.SUBSCR_NAMESPACE_AQ.

The protocol parameter specifies the protocol to use when notifications are sent. Currently the only valid value is oracledb.SUBSCR_PROTO_OCI.

The callback is expected to be a callable that accepts a single parameter. A message object is passed to this callback whenever a notification is received.

The timeout value specifies that the subscription expires after the given time in seconds. The default value of 0 indicates that the subscription never expires.

The operations parameter enables filtering of the messages that are sent (insert, update, delete). The default value will send notifications for all operations. This parameter is only used when the namespace is set to oracledb.SUBSCR_NAMESPACE_DBCHANGE.

The port parameter specifies the listening port for callback notifications from the database server. If not specified, an unused port will be selected by the Oracle Client libraries.

The qos parameter specifies quality of service options. It should be one or more of the following flags, OR’ed together: oracledb.SUBSCR_QOS_RELIABLE, oracledb.SUBSCR_QOS_DEREG_NFY, oracledb.SUBSCR_QOS_ROWIDS, oracledb.SUBSCR_QOS_QUERY, oracledb.SUBSCR_QOS_BEST_EFFORT.

The ip_address parameter specifies the IP address (IPv4 or IPv6) in standard string notation to bind for callback notifications from the database server. If not specified, the client IP address will be determined by the Oracle Client libraries.

The grouping_class parameter specifies what type of grouping of notifications should take place. Currently, if set, this value can only be set to the value oracledb.SUBSCR_GROUPING_CLASS_TIME, which will group notifications by the number of seconds specified in the grouping_value parameter. The grouping_type parameter should be one of the values oracledb.SUBSCR_GROUPING_TYPE_SUMMARY (the default) or oracledb.SUBSCR_GROUPING_TYPE_LAST.

The name parameter is used to identify the subscription and is specific to the selected namespace. If the namespace parameter is oracledb.SUBSCR_NAMESPACE_DBCHANGE then the name is optional and can be any value. If the namespace parameter is oracledb.SUBSCR_NAMESPACE_AQ, however, the name must be in the format ‘<QUEUE_NAME>’ for single consumer queues and ‘<QUEUE_NAME>:<CONSUMER_NAME>’ for multiple consumer queues, and identifies the queue that will be monitored for messages. The queue name may include the schema, if needed.

The client_initiated parameter is used to determine if client initiated connections or server initiated connections (the default) will be established. Client initiated connections are only available in Oracle Client 19.4 and Oracle Database 19.4 and higher.

For consistency and compliance with the PEP 8 naming style, the parameter ipAddress was renamed to ip_address, the parameter groupingClass was renamed to grouping_class, the parameter groupingValue was renamed to grouping_value, the parameter groupingType was renamed to grouping_type and the parameter clientInitiated was renamed to client_initiated. The old names will continue to work as keyword parameters for a period of time.

Note

This method is an extension to the DB API definition.

Note

The subscription can be deregistered in the database by calling the function unsubscribe(). If this method is not called and the connection that was used to create the subscription is explicitly closed using the function close(), the subscription will not be deregistered in the database.

Connection.tpc_begin(xid, flags, timeout)

Begins a Two-Phase Commit (TPC) on a global transaction using the specified transaction identifier (xid).

The xid parameter should be an object returned by the xid() method.

The flags parameter is one of the constants oracledb.TPC_BEGIN_JOIN, oracledb.TPC_BEGIN_NEW, oracledb.TPC_BEGIN_PROMOTE, or oracledb.TPC_BEGIN_RESUME. The default is oracledb.TPC_BEGIN_NEW.

The timeout parameter is the number of seconds to wait for a transaction to become available for resumption when TPC_BEGIN_RESUME is specified in the flags parameter. When TPC_BEGIN_NEW is specified in the flags parameter, the timeout parameter indicates the number of seconds the transaction can be inactive before it is automatically terminated by the system. A transaction is inactive between the time it is detached with Connection.tpc_end() and the time it is resumed with Connection.tpc_begin().The default is 0 seconds.

The following code sample demonstrates the tpc_begin() function:

x = connection.xid(format_id=1, global_transaction_id="tx1", branch_qualifier="br1")
connection.tpc_begin(xid=x, flags=oracledb.TPC_BEGIN_NEW, timeout=30)

See Using Two-Phase Commits (TPC) for information on TPC.

Connection.tpc_commit(xid, one_phase)

Commits a global transaction. When called with no arguments, this method commits a transaction previously prepared with tpc_begin() and optionally prepared with tpc_prepare(). If tpc_prepare() is not called, a single phase commit is performed. A transaction manager may choose to do this if only a single resource is participating in the global transaction.

If an xid parameter is passed, then an object should be returned by the xid() function. This form should be called outside of a transaction and is intended for use in recovery.

The one_phase parameter is a boolean identifying whether to perform a one-phase or two-phase commit. If one_phase parameter is True, a single-phase commit is performed. The default value is False. This parameter is only examined if a value is provided for the xid parameter. Otherwise, the driver already knows whether tpc_prepare() was called for the transaction and whether a one-phase or two-phase commit is required.

The following code sample demonstrates the tpc_commit() function:

x = connection.xid(format_id=1, global_transaction_id="tx1", branch_qualifier="br1")
connection.tpc_commit(xid=x, one_phase=False)

See Using Two-Phase Commits (TPC) for information on TPC.

Connection.tpc_end(xid, flags)

Ends or suspends work on a global transaction. This function is only intended for use by transaction managers.

If an xid parameter is passed, then an object should be returned by the xid() function. If no xid parameter is passed, then the transaction identifier used by the previous tpc_begin() is used.

The flags parameter is one of the constants oracledb.TPC_END_NORMAL or oracledb.TPC_END_SUSPEND. The default is oracledb.TPC_END_NORMAL.

If the flag is oracledb.TPC_END_SUSPEND then the transaction may be resumed later by calling Connection.tpc_begin() with the flag oracledb.TPC_BEGIN_RESUME.

The following code sample demonstrates the tpc_end() function:

x = connection.xid(format_id=1, global_transaction_id="tx1", branch_qualifier="br1")
connection.tpc_end(xid=x, flags=oracledb.TPC_END_NORMAL)

See Using Two-Phase Commits (TPC) for information on TPC.

Connection.tpc_forget(xid)

Causes the database to forget a heuristically completed TPC transaction. This function is only intended to be called by transaction managers.

The xid parameter is mandatory and should be an object should be returned by the xid() function.

The following code sample demonstrates the tpc_forget() function:

x = connection.xid(format_id=1, global_transaction_id="tx1", branch_qualifier="br1")
connection.tpc_forget(xid=x)

See Using Two-Phase Commits (TPC) for information on TPC.

Connection.tpc_prepare(xid)

Prepares a two-phase transaction for commit. After this function is called, no further activity should take place on this connection until either tpc_commit() or tpc_rollback() have been called.

Returns a boolean indicating whether a commit is needed or not. If you attempt to commit when not needed, then it results in the error ORA-24756: transaction does not exist.

If an xid parameter is passed, then an object should be returned by the xid() function. If an xid parameter is not passed, then the transaction identifier used by the previous tpc_begin() is used.

The following code sample demonstrates the tpc_prepare() function:

x = connection.xid(format_id=1, global_transaction_id="tx1", branch_qualifier="br1")
connection.tpc_prepare(xid=x)

See Using Two-Phase Commits (TPC) for information on TPC.

Connection.tpc_recover()

Returns a list of pending transaction identifiers that require recovery. Objects of type Xid (as returned by the xid() function) are returned and these can be passed to tpc_commit() or tpc_rollback() as needed.

This function queries the view DBA_PENDING_TRANSACTIONS and requires SELECT privilege on that view.

The following code sample demonstrates the tpc_recover() function:

connection.tpc_recover()

See Using Two-Phase Commits (TPC) for information on TPC.

Connection.tpc_rollback(xid)

Rolls back a global transaction.

If an xid parameter is not passed, then it rolls back the transaction that was previously started with tpc_begin().

If an xid parameter is passed, then an object should be returned by xid() and the specified transaction is rolled back. This form should be called outside of a transaction and is intended for use in recovery.

The following code sample demonstrates the tpc_rollback() function:

x = connection.xid(format_id=1, global_transaction_id="tx1", branch_qualifier="br1")
connection.tpc_rollback(xid=x)

See Using Two-Phase Commits (TPC) for information on TPC.

Connection.unsubscribe(subscr): Unsubscribe from events in the database that were originally subscribed to using subscribe(). The connection used to unsubscribe should be the same one used to create the subscription, or should access the same database and be connected as the same user name.

Connection.xid(format_id, global_transaction_id, branch_qualifier)

Returns a global transaction identifier (xid) that can be used with the Two-Phase Commit (TPC) functions.

The xid contains a format identifier, a global transaction identifier, and a branch identifier. There are no checks performed at the Python level. The values are checked by ODPI-C when they are passed to the relevant functions. .. When this functionality is also supported in the thin driver the checks will be performed at the Python level as well.

The format_id parameter should be a positive 32-bit integer. This value identifies the format of the global_transaction_id and branch_qualifier parameters and the value is determined by the Transaction Manager (TM), if one is in use.

The global_transaction_id and branch_qualifier parameters should be of type bytes or string. If a value of type string is passed, then this value will be UTF-8 encoded to bytes. The values cannot exceed 64 bytes in length.

The following code sample demonstrates the xid() function:

connection.xid(format_id=1, global_transaction_id="tx1", branch_qualifier="br1")

See Using Two-Phase Commits (TPC) for information on TPC.

3.2. Connection Attributes

Connection.action: This write-only attribute sets the action column in the v$session table. It is a string attribute but the value None is accepted and treated as an empty string.

Note

This attribute is an extension to the DB API definition.

Connection.autocommit: This read-write attribute determines whether autocommit mode is on or off. When autocommit mode is on, all statements are committed as soon as they have completed executing.

Note

This attribute is an extension to the DB API definition.

Connection.call_timeout

This read-write attribute specifies the amount of time (in milliseconds) that a single round-trip to the database may take before a timeout will occur. A value of 0 means that no timeout will take place.

If a timeout occurs, the error DPI-1067 will be returned if the connection is still usable. Alternatively the error DPI-1080 will be returned if the connection has become invalid and can no longer be used.

For consistency and compliance with the PEP 8 naming style, the attribute callTimeout was renamed to call_timeout. The old name will continue to work for a period of time. The error DPI-1080 was also introduced in this release.

Note

This attribute is an extension to the DB API definition and is only available in Oracle Client 18c and higher.

Connection.client_identifier: This write-only attribute sets the client_identifier column in the v$session table.

Note

This attribute is an extension to the DB API definition.

Connection.clientinfo: This write-only attribute sets the client_info column in the v$session table.

Note

This attribute is an extension to the DB API definition.

Connection.current_schema: This read-write attribute sets the current schema attribute for the session. Setting this value is the same as executing the SQL statement ALTER SESSION SET CURRENT_SCHEMA. The attribute is set (and verified) on the next call that does a round trip to the server. The value is placed before unqualified database objects in SQL statements you then execute.

Note

This attribute is an extension to the DB API definition.

Connection.db_domain: This read-only attribute specifies the Oracle Database domain name associated with the connection. It is the same value returned by the SQL SELECT value FROM V$PARAMETER WHERE NAME = 'db_domain'.

New in version 2.0.0.

Note

This attribute is an extension to the DB API definition.

Connection.db_name: This read-only attribute specifies the Oracle Database name associated with the connection. It is the same value returned by the SQL SELECT NAME FROM V$DATABASE.

New in version 2.0.0.

Note

This attribute is an extension to the DB API definition.

Connection.dbop: This write-only attribute sets the database operation that is to be monitored. This can be viewed in the DBOP_NAME column of the v$sql_monitor table.

Note

This attribute is an extension to the DB API definition.

Connection.dsn: This read-only attribute returns the TNS entry of the database to which a connection has been established.

Note

This attribute is an extension to the DB API definition.

Connection.econtext_id: This write-only attribute specifies the execution context id. This value can be found as ecid in the v$session table and econtext_id in the auditing tables. The maximum length is 64 bytes.

Connection.edition: This read-only attribute gets the session edition and is only available in Oracle Database 11.2 (both client and server must be at this level or higher for this to work).

Note

This attribute is an extension to the DB API definition.

Connection.external_name: This read-write attribute specifies the external name that is used by the connection when logging distributed transactions.

Note

This attribute is an extension to the DB API definition.

Connection.handle

This read-only attribute returns the Oracle Call Interface (OCI) service context handle for the connection. It is primarily provided to facilitate testing the creation of a connection using the OCI service context handle.

This property is only relevant in the python-oracledb Thick mode.

Note

This attribute is an extension to the DB API definition.

Connection.inputtypehandler: This read-write attribute specifies a method called for each value that is bound to a statement executed on any cursor associated with this connection. The method signature is handler(cursor, value, arraysize) and the return value is expected to be a variable object or None in which case a default variable object will be created. If this attribute is None, the default behavior will take place for all values bound to statements.

Note

This attribute is an extension to the DB API definition.

Connection.instance_name: This read-only attribute specifies the Oracle Database instance name associated with the connection. It is the same value as the SQL expression sys_context('userenv', 'instance_name').

New in version 1.4.0.

Note

This attribute is an extension to the DB API definition.

Connection.internal_name: This read-write attribute specifies the internal name that is used by the connection when logging distributed transactions.

Note

This attribute is an extension to the DB API definition.

Connection.ltxid: This read-only attribute returns the logical transaction id for the connection. It is used within Oracle Transaction Guard as a means of ensuring that transactions are not duplicated. See the Oracle documentation and the provided sample for more information.

Connection.max_open_cursors: This read-only attribute specifies the maximum number of cursors that the database can have open concurrently. It is the same value returned by the SQL SELECT VALUE FROM V$PARAMETER WHERE NAME = 'open_cursors'.

New in version 2.0.0.

Note

This attribute is an extension to the DB API definition.

Connection.module: This write-only attribute sets the module column in the v$session table. The maximum length for this string is 48 and if you exceed this length you will get ORA-24960.

Connection.outputtypehandler

This read-write attribute specifies a method called for each column that is going to be fetched from any cursor associated with this connection. The method signature is handler(cursor, metadata) and the return value is expected to be a variable object or None in which case a default variable object will be created. If this attribute is None, the default behavior will take place for all columns fetched from cursors.

See Changing Fetched Data Types with Output Type Handlers.

Changed in version 1.4: The method signature was changed. The previous signature handler(cursor, name, default_type, length, precision, scale) will still work but is deprecated and will be removed in a future version.

Note

This attribute is an extension to the DB API definition.

Connection.proxy_user: This read-only attribute returns the name of the user which was used as a proxy when creating the connection to the database.

New in version 2.0.0.

Note

This attribute is an extension to the DB API definition.

Connection.sdu: This read-only attribute specifies the size of the Session Data Unit (SDU) that is being used by the connection. The value will be the lesser of the requested python-oracledb size and the maximum size allowed by the database network configuration. It is available only in the python-oracledb Thin mode.

New in version 2.0.0.

Note

This attribute is an extension to the DB API definition.

Connection.service_name: This read-only attribute specifies the Oracle Database service name associated with the connection. This is the same value returned by the SQL SELECT SYS_CONTEXT('USERENV', 'SERVICE_NAME') FROM DUAL.

New in version 2.0.0.

Note

This attribute is an extension to the DB API definition.

Connection.stmtcachesize

This read-write attribute specifies the size of the statement cache. This value can make a significant difference in performance if you have a small number of statements that you execute repeatedly.

The default value is 20.

See Statement Caching for more information.

Note

This attribute is an extension to the DB API definition.

Connection.tag

This read-write attribute initially contains the actual tag of the session that was acquired from a pool by ConnectionPool.acquire(). If the connection was not acquired from a pool or no tagging parameters were specified (tag and matchanytag) when the connection was acquired from the pool, this value will be None. If the value is changed, it must be a string containing name=value pairs like “k1=v1;k2=v2”.

If this value is not None when the connection is released back to the pool it will be used to retag the session. This value can be overridden in the call to ConnectionPool.release().

Note

This attribute is an extension to the DB API definition.

Connection.thin: This read-only attribute returns a boolean indicating if the connection was established with the python-oracledb Thin mode (True) or python-oracledb Thick mode (False).

Note

This attribute is an extension to the DB API definition.

Connection.transaction_in_progress: This read-only attribute specifies whether a transaction is currently in progress on the database associated with the connection.

New in version 2.0.0.

Note

This attribute is an extension to the DB API definition.

Connection.username: This read-only attribute returns the name of the user which established the connection to the database.

Note

This attribute is an extension to the DB API definition.

Connection.version: This read-only attribute returns the version of the database to which a connection has been established.

Note

This attribute is an extension to the DB API definition.

Note

If you connect to Oracle Database 18 or higher using Oracle Client libraries 12.2 or lower you will only receive the base version (such as 18.0.0.0.0) instead of the full version (such as 18.3.0.0.0).

Connection.warning

This read-only attribute provides an oracledb._Error object giving information about any database warnings (such as the password being in the grace period, or the pool being created with a smaller than requested size due to database resource restrictions) that were generated during connection establishment or by oracledb.create_pool(). The attribute will be present if there was a warning, but creation otherwise completed successfully. The connection will be usable despite the warning.

For standalone connections, Connection.warning will be present for the lifetime of the connection.

For pooled connections, Connection.warning will be cleared when a connection is released to the pool such as with ConnectionPool.release().

In python-oracledb Thick mode, warnings may be generated during pool creation itself. These warnings will be placed on new connections created by the pool, provided no warnings were generated by the individual connection creations, in which case those connection warnings will be returned.

If no warning was generated the value None is returned.

New in version 2.0.0.

Note

This attribute is an extension to the DB API definition.