HISAM copies (DFSURUL0 and DFSURRL0)

Using the HISAM Reorganization Unload utility (DFSURUL0) to make backup copies of a database allows you to process an entire HISAM database in one pass (the image copy utilities deal with single data sets or areas). The unload utility (DFSURUL0) also reorganizes the database as it copies it.

Because the unload utility (DFSURUL0) reorganizes the database, before resuming normal online operations, the data set must be reloaded using the HISAM Reorganization Reload utility (DFSURRL0). The logging, which is done between the unload and reload, reflects the old data set organization.

When using the HISAM utility to make a backup copy, reload immediately, or the actual database and the backup database are mismatched.

The reload utility (DFSURRL0) notifies DBRC. The unload utility creates a reorganized copy of each data set. Then the reload utility reloads each data set from the reorganized copy, and through DBRC, creates a REORG and an IC record in the RECON data set for each data set. The IC record points to the data set that was output from the Unload utility and input to the Reload utility. After a database has been reorganized, a DBDS can be authorized only if an image copy of that data set has been created.

Updates of the database between unload and reload operations must be prevented. Updates of the database made after an unload operation but before a reload operation are wiped-out by the reload operation. In addition, the change records that are logged reflect the old organization, so that a subsequent recovery using those log records damages the database.

You can prevent access to a shared database during reorganization by using one of the following methods:

• From an online IMS subsystem, issue a global /DBRECOVERY command for the database that is to be reorganized. This prevents any subsequent authorizations except for reorganization and recovery. Ensure that recovery utilities do not run during the reorganization.
• Manually update the RECON data set by specifying the NOAUTH parameter of the CHANGE.DB command. This prevents any subsequent authorizations except for the reorganization and recovery utilities. Ensure that recovery utilities do not run during the reorganization. After the reorganization process is complete, manually update the RECON data set by specifying the AUTH parameter of the CHANGE.DB command for the database that was just reorganized.