The RECOVERY_UNITS and DA_LOGS catalog tables are located in the database's catalog space. RECOVERY_UNITS contains entries for the SESAM backup copies of the user spaces; DA_LOGS contains information on the DA-LOG files.
Refer to section “Files and tables used for media recovery” for a detailed description of the RECOVERY_UNITS and DA_LOGS tables.
The CAT-REC file (catalog recovery file) contains recovery unit records for the catalog space and the associated CAT-LOG records.
Refer to section “CAT-REC file” for a detailed description of the CAT-REC file.
Using the utility statement MODIFY, the database administrator can do the following:
Delete records in the catalog table RECOVERY_UNITS which pertain to the SESAM backup copies of a specific user space.
At least the last two records are alwas retained. One of the remaining records refers to the SESAM backup copy of the user space that was created last. Otherwise all remaining records, or records of a specific age, are deleted for this user space.
Delete records in the catalog tables RECOVERY_UNITS and DA_LOGS independently of their assignment to specific user spaces.
At least the last two records per user space are retained in RECOVERY_UNITS. One of the remaining records refers to the SESAM backup copy of the user space which was created last. Otherwise all remaining records, or records of a specific age are deleted from RECOVERY_UNITS.
In DA_LOGS, only those records are not deleted that pertain to DA-LOG files that follow on from SESAM backup copies for which RECOVERY_UNITS still contains records after a MODIFY.Foreign copies represent a special case here. When you work with foreign copies, no new records are created in the RECOVERY_UNITS table. You can specify the UNRESTRICTED clause in order to delete records from the DA_LOGS catalog table. Records are then deleted from DA_LOGS whether or not there is a last
RECOVERY_UNITS record.UNRESTRICTED deletes all the records with the specified age in the RECOVERY_UNITS and DA_LOGS, up to but excluding the last in each case. This record is retained for technical reasons.
A RECOVER is no longer possible if the required files have been deleted in the catalog tables RECOVERY_UNITS and DA_LOGS. The oldest record in DA_LOGS required for a foreign copy of a space is the record that was created in the space when it was closed after the last update. If the foreign copy is generated during or after a session in which the space was not opened or was used for read access only then the restart point is not updated in the space.In the current CAT-REC file, delete recovery unit records and CAT-LOG records which refer to SESAM backup copies of the catalog space.
The latest recovery unit record and the associated CAT-LOG record are retained in the CAT-REC file so that a recovery is still possible with SESAM/SQL. All other records or records of a particular age can be deleted.
Foreign copies represent a special case here. When you work with foreign copies, no recovery unit records are created in the CAT-REC file. CAT-LOG records cannot be deleted without the corresponding recover unit record.