Summary of DBMS_TRANSACTION Subprograms

Table 75-1 DBMS_TRANSACTION Subprograms

Subprogram
READ_ONLY Procedure
READ_WRITE Procedure
ADVISE_ROLLBACK Procedure
ADVISE_NOTHING Procedure
ADVISE_COMMIT Procedure
USE_ROLLBACK_SEGMENT Procedure
COMMIT_COMMENT Procedure
COMMIT_FORCE Procedure
COMMIT Procedure
SAVEPOINT Procedure
ROLLBACK Procedure
ROLLBACK_SAVEPOINT Procedure
ROLLBACK_FORCE Procedure
BEGIN_DISCRETE_TRANSACTION Procedure
PURGE_MIXED Procedure
PURGE_LOST_DB_ENTRY Procedure
LOCAL_TRANSACTION_ID Function
STEP_ID Function

READ_ONLY Procedure

This procedure is equivalent to following SQL statement:

SET TRANSACTION READ ONLY

Syntax

DBMS_TRANSACTION.READ_ONLY;

READ_WRITE Procedure

This procedure is equivalent to following SQL statement:

SET TRANSACTION READ WRITE

Syntax

DBMS_TRANSACTION.READ_WRITE;

ADVISE_ROLLBACK Procedure

This procedure is equivalent to following SQL statement:

ALTER SESSION ADVISE ROLLBACK

Syntax

DBMS_TRANSACTION.ADVISE_ROLLBACK;

ADVISE_NOTHING Procedure

This procedure is equivalent to following SQL statement:

ALTER SESSION ADVISE NOTHING

Syntax

DBMS_TRANSACTION.ADVISE_NOTHING;

ADVISE_COMMIT Procedure

This procedure is equivalent to following SQL statement:

ALTER SESSION ADVISE COMMIT

Syntax

DBMS_TRANSACTION.ADVISE_COMMIT;

USE_ROLLBACK_SEGMENT Procedure

This procedure is equivalent to following SQL statement:

SET TRANSACTION USE ROLLBACK SEGMENT <rb_seg_name>

Syntax

DBMS_TRANSACTION.USE_ROLLBACK_SEGMENT (
   rb_name VARCHAR2);

Parameters

Table 75-2 USE_ROLLBACK_SEGMENT Procedure Parameters

Parameter	Description
rb_name	Name of rollback segment to use.

COMMIT_COMMENT Procedure

This procedure is equivalent to following SQL statement:

COMMIT COMMENT <text>

Syntax

DBMS_TRANSACTION.COMMIT_COMMENT (
   cmnt VARCHAR2);

Parameters

Table 75-3 COMMIT_COMMENT Procedure Parameters

Parameter	Description
cmnt	Comment to associate with this commit.

COMMIT_FORCE Procedure

This procedure is equivalent to following SQL statement:

COMMIT FORCE <text>, <number>"

Syntax

DBMS_TRANSACTION.COMMIT_FORCE (
   xid VARCHAR2, 
   scn VARCHAR2 DEFAULT NULL);

Parameters

Table 75-4 COMMIT_FORCE Procedure Parameters

Parameter	Description
xid	Local or global transaction ID.
scn	System change number.

COMMIT Procedure

This procedure is equivalent to following SQL statement:

COMMIT 

Here for completeness. This is already implemented as part of PL/SQL.

Syntax

DBMS_TRANSACTION.COMMIT;

SAVEPOINT Procedure

This procedure is equivalent to following SQL statement:

SAVEPOINT <savepoint_name>

Here for completeness. This is already implemented as part of PL/SQL.

Syntax

DBMS_TRANSACTION.SAVEPOINT (
   savept VARCHAR2);

Parameters

Table 75-5 SAVEPOINT Procedure Parameters

Parameter	Description
savept	Savepoint identifier.

ROLLBACK Procedure

This procedure is equivalent to following SQL statement:

ROLLBACK

Here for completeness. This is already implemented as part of PL/SQL.

Syntax

DBMS_TRANSACTION.ROLLBACK;

ROLLBACK_SAVEPOINT Procedure

This procedure is equivalent to following SQL statement:

ROLLBACK TO SAVEPOINT <savepoint_name>

Here for completeness. This is already implemented as part of PL/SQL.

Syntax

DBMS_TRANSACTION.ROLLBACK_SAVEPOINT (
   savept VARCHAR2);

Parameters

Table 75-6 ROLLBACK_SAVEPOINT Procedure Parameters

Parameter	Description
savept	Savepoint identifier.

ROLLBACK_FORCE Procedure

This procedure is equivalent to following SQL statement:

ROLLBACK FORCE <text>

Syntax

DBMS_TRANSACTION.ROLLBACK_FORCE (
   xid VARCHAR2);

Parameters

Table 75-7 ROLLBACK_FORCE Procedure Parameters

Parameter	Description
xid	Local or global transaction ID.

BEGIN_DISCRETE_TRANSACTION Procedure

This procedure sets "discrete transaction mode" for this transaction.

Syntax

DBMS_TRANSACTION.BEGIN_DISCRETE_TRANSACTION;

Exceptions

Table 75-8 BEGIN_DISCRETE_TRANSACTION Procedure Exceptions

Exception	Description
ORA-08175	A transaction attempted an operation which cannot be performed as a discrete transaction. If this exception is encountered, then rollback and retry the transaction
ORA-08176	A transaction encountered data changed by an operation that does not generate rollback data: create index, direct load or discrete transaction. If this exception is encountered, then retry the operation that received the exception.

Example

DISCRETE_TRANSACTION_FAILED exception;
    pragma exception_init(DISCRETE_TRANSACTION_FAILED, -8175);
CONSISTENT_READ_FAILURE exception;
    pragma exception_init(CONSISTENT_READ_FAILURE, -8176); 

PURGE_MIXED Procedure

When in-doubt transactions are forced to commit or rollback (instead of letting automatic recovery resolve their outcomes), there is a possibility that a transaction can have a mixed outcome: Some sites commit, and others rollback. Such inconsistency cannot be resolved automatically by Oracle; however, Oracle flags entries in DBA_2PC_PENDING by setting the MIXED column to a value of 'yes'.

Oracle never automatically deletes information about a mixed outcome transaction. When the application or DBA is certain that all inconsistencies that might have arisen as a result of the mixed transaction have been resolved, this procedure can be used to delete the information about a given mixed outcome transaction.

Syntax

DBMS_TRANSACTION.PURGE_MIXED (
   xid VARCHAR2);

Parameters

Table 75-9 PURGE_MIXED Procedure Parameters

Parameter	Description
xid	Must be set to the value of the LOCAL_TRAN_ID column in the DBA_2PC_PENDING table.

PURGE_LOST_DB_ENTRY Procedure

When a failure occurs during commit processing, automatic recovery consistently resolves the results at all sites involved in the transaction. However, if the remote database is destroyed or re-created before recovery completes, then the entries used to control recovery in DBA_2PC_PENDING and associated tables are never removed, and recovery will periodically retry. Procedure PURGE_LOST_DB_ENTRY enables removal of such transactions from the local site.

Syntax

DBMS_TRANSACTION.PURGE_LOST_DB_ENTRY (
   xid VARCHAR2);

Before automatic recovery runs, the transaction may show up in DBA_2PC_PENDING as state "collecting", "committed", or "prepared". If the DBA has forced an in-doubt transaction to have a particular result by using "commit force" or "rollback force", then states "forced commit" or "forced rollback" may also appear. Automatic recovery normally deletes entries in any of these states. The only exception is when recovery finds a forced transaction which is in a state inconsistent with other sites in the transaction; in this case, the entry is left in the table and the MIXED column has the value 'yes'.

However, under certain conditions, it may not be possible for automatic recovery to run. For example, a remote database may have been permanently lost. Even if it is re-created, it gets a new database ID, so that recovery cannot identify it (a possible symptom is ORA-02062). In this case, the DBA may use the procedure PURGE_LOST_DB_ENTRY to clean up the entries in any state other than "prepared". The DBA does not need to be in any particular hurry to resolve these entries, because they are not holding any database resources.

The following table indicates what the various states indicate about the transaction and what the DBA actions should be:

Table 75-10 PURGE_LOST_DB_ENTRY Procedure States

State of Column	State of Global Transaction	State of Local Transaction	Normal DBA Action	Alternative DBA Action
Collecting	Rolled back	Rolled back	None	PURGE_LOST_DB_ENTRY (See Note 1)
Committed	Committed	Committed	None	PURGE_LOST_DB_ENTRY (See Note 1)
Prepared	Unknown	Prepared	None	FORCE COMMIT or ROLLBACK
Forced commit	Unknown	Committed	None	PURGE_LOST_DB_ENTRY (See Note 1)
Forced rollback	Unknown	Rolled back	None	PURGE_LOST_DB_ENTRY (See Note 1)
Forced commit (mixed)	Mixed	Committed	(See Note 2)
Forced rollback (mixed)	Mixed	Rolled back	(See Note 2)

Parameters

Table 75-11 PURGE_LOST_DB_ENTRY Procedure Parameters

Parameter	Description
xid	Must be set to the value of the LOCAL_TRAN_ID column in the DBA_2PC_PENDING table.

LOCAL_TRANSACTION_ID Function

This function returns the local (to instance) unique identifier for current transaction. It returns null if there is no current transaction.

Syntax

DBMS_TRANSACTION.LOCAL_TRANSACTION_ID (
   create_transaction BOOLEAN := FALSE)
  RETURN VARCHAR2;

Parameters

Table 75-12 LOCAL_TRANSACTION_ID Function Parameters

Parameter	Description
create_transaction	If true, then start a transaction if one is not currently active.

STEP_ID Function

This function returns local (to local transaction) unique positive integer that orders the DML operations of a transaction.

Syntax

DBMS_TRANSACTION.STEP_ID 
   RETURN NUMBER;