BACKOUT DURATION field (BACKODUR subsystem parameter)
The BACKODUR subsystem parameter is used to calculate the number of log records that are to be backed out during a restart. This value is applied when the LIMIT BACKOUT field is set to AUTO, YES, LIGHT, or LIGHTAUTO.
| Acceptable values: | 0–255 |
|---|---|
| Default: | 5 |
| Update: | option 42 on panel DSNTIPB |
| DSNZPxxx: | DSN6SYSP BACKODUR |
During a restart, backward-log processing continues until the following events occur:
- All inflight and in-abort URs with update activity against the catalog or directory are backed out.
- All inflight and in-abort URs that only update temporary tables are backed out.
- The number of processed log records equals the number specified in the BACKOUT DURATION field multiplied by the number of log records per checkpoint. If the CHECKPOINT TYPE field is set to LOGRECS or BOTH, the value of the RECORDS/CHECKPOINT field is used as the number of log records per checkpoint. If the CHECKPOINT TYPE field is set to MINUTES, the default value of 500000 is used as the number of log records per checkpoint.
Inflight and in-abort URs that are not completely backed out during restart are converted to postponed-abort status. Sets or partitions with postponed backout work are put into restart-pending (RESTP) state. This state blocks most access to the object. The exceptions are access by the RECOVER POSTPONED command state or by automatic backout processing that Db2 performs when the LIMIT BACKOUT field is set to AUTO or LIGHTAUTO.
A table space might be in restart-pending mode, without the associated index spaces also in restart-pending mode. This happens if a postponed-abort UR makes updates only to non-indexed fields of a table in a table space. In this case, the indexes are accessible to SQL (for index-only queries), even though the table space is inaccessible.