2.316 PRIORITY_TXNS_MODE
PRIORITY_TXNS_MODE
specifies the mode for Priority Transactions.
Property | Description |
---|---|
Parameter type |
String |
Syntax |
|
Default value |
|
Modifiable |
|
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 aHIGH
priority transaction will wait for a row lock -
PRIORITY_TXNS_MEDIUM_WAIT_TARGET
- Specifies the maximum number of seconds that aMEDIUM
priority transaction will wait for a row lock -
TXN_PRIORITY
- Specifies a priority (HIGH
,MEDIUM
, orLOW
) 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 enablingROLLBACK
mode.The database determines when
HIGH
andMEDIUM
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 Database 23ai.
See Also:
-
Oracle Database Administrator’s Guide for more information about Priority Transactions