U LOCK FOR RR/RS field (RRULOCK subsystem parameter)
When operations use repeatable read (RR) or read stability (RS) isolation levels to access a table, a specified locking method is used. The RRULOCK subsystem parameter specifies whether Db2 is to use U (UPDATE) locks or S (SHARE) locks.
| Acceptable values: | YES, NO |
|---|---|
| Default: | YES |
| Update: | option 32 on panel DSNTIPB |
| DSNZPxxx: | DSN6SPRM RRULOCK |
- YES
- The lock mode for operations with RR or RS isolation levels is U. If your applications make frequent updates with repeatable-read isolation, the U-lock might provide greater concurrency than the S-lock. However, applications that require high concurrency are almost always more efficient if they use cursor stability (CS) isolation.
- NO
- The lock mode for operations with RR or RS isolation levels is S. If the cursor in your applications includes the FOR UPDATE OF clause, but updates are infrequent, S-locks generally provide better performance.