PRIORITY_TXNS_MODE

PRIORITY_TXNS_MODE specifies the mode for Priority Transactions.

Property	Description
Parameter type	String
Syntax	PRIORITY_TXNS_MODE = { ROLLBACK | TRACK }
Default value	ROLLBACK
Modifiable	ALTER SYSTEM
Modifiable in a PDB	Yes
Basic	No
Oracle RAC	Multiple instances must have the same value.

Values:

• ROLLBACK - This setting enables Priority Transactions. The database will automatically roll back low-priority transactions that are blocking higher priority transactions from obtaining row locks.

  Before enabling Priority Transactions, ensure that the following initialization parameters are configured properly:

  • PRIORITY_TXNS_HIGH_WAIT_TARGET - Specifies the maximum number of seconds that a HIGH priority transaction will wait for a row lock

  • PRIORITY_TXNS_MEDIUM_WAIT_TARGET - Specifies the maximum number of seconds that a MEDIUM priority transaction will wait for a row lock

  • TXN_PRIORITY - Specifies a priority (HIGH, MEDIUM, or LOW) for all transactions in a user session

  When running in ROLLBACK mode, you can track the performance of Priority Transactions by monitoring the following statistics:

  • txns rollback priority_txns_high_wait_target

  • txns rollback priority_txns_medium_wait_target

• TRACK - This setting allows you to track the potential behavior of Priority Transactions. You can use this mode to tune the Priority Transactions initialization parameters before enabling ROLLBACK mode.

  The database determines when HIGH and MEDIUM priority transactions would be rolled back, given the current values of the Priority Transactions initialization parameters. However, instead of actually rolling back the transactions, the database only increments the following statistics:

  • txns track mode priority_txns_high_wait_target

  • txns track mode priority_txns_medium_wait_target

  You can also monitor the following wait events to determine the amount of time transactions are waiting for row locks:

  • enq: TX - row lock (HIGH priority)

  • enq: TX - row lock (MEDIUM priority)

  • enq: TX - row lock (LOW priority)

Note: This parameter is available starting with Oracle AI Database 26ai.

See Also:

• “PRIORITY_TXNS_HIGH_WAIT_TARGET”

• “PRIORITY_TXNS_MEDIUM_WAIT_TARGET”

• “TXN_PRIORITY”

• Oracle AI Database Administrator’s Guide for more information about Priority Transactions