HISAM copies (DFSURUL0 and DFSURRL0)

The HISAM Reorganization Unload utility (DFSURUL0) can make backup copies of an entire HISAM database while it reorganizes the database, all in one pass.

Because the unload utility (DFSURUL0) reorganizes the database, you must, before resuming normal online operations, reload the data set using the HISAM Reorganization Reload utility (DFSURRL0), as shown in the following figure. If you do not reload the data set, the logging done after unload but before reload reflects the old organization of the data set. Therefore, if you need to use that log to recover the data set in the future, the organizations will not match, and the data set's integrity will be destroyed.

Figure 1. Making a backup copy with HISAM unload
This figure illustrates the use of the HISAM utility to make a backup copy.

When using the HISAM utility to make a backup copy, you must reload immediately, or the actual database will not match the backup database. The reload utility (DFSURRL0) uses the output of its reorganization step as input to the reload step as if it were an image copy data set. After reorganizing a database, you must make an image copy of it before you can authorize the DBDS.

Before reorganizing a shared database, you must prevent other subsystems from being authorized during the reorganization process by:

  • Issuing a global /DBRECOVERY DB or UPDATE DB STOP(ACCESS) command for the database to be reorganized. The /DBRECOVERY DB GLOBAL command prevents further authorizations except for reorganization and recovery utilities.
  • Issuing the CHANGE.DB command with the NOAUTH keyword to manually update the RECON data set. This command prevents future authorizations except for the reorganization and recovery utilities. After the reorganization is complete, manually update the RECON data set by issuing the CHANGE.DB command with the AUTH keyword for the database that was just reorganized.

Recommendation: Ensure that recovery utilities do not run during the reorganization.