Using the RBA0 backup detection feature

This topic describes the RBA0 backup detection feature.

Overview of the RBA0 backup detection feature

Many organizations use KSDS or ESDS files for data-entry purposes. These files are typically cleared of all data by using an IDCAMS delete/define operation, followed by the load of a dummy record to the file. The file is then opened to CICS and data is entered by online operators. This process is repeated one or more times a day. There is no relationship between sets of data records other than that the records are stored under the same VSAM data set name.

RBA0 backups

The RUV RBA0 backup detection feature registers a backup of a file at the point in time when the file was empty. It can also create an RBA0 backup when a file that has been defined with the REUSE option is opened for output. This action causes the high used relative byte address (RBA) to be reset to zero, which effectively deletes all records in the file.

An RBA0 backup is simply a record in the repository; no physical data set is associated with an RBA0 backup. However, an RBA0 backup is intended to be used, in the same way as any other type of backup, as a starting point for recovery. When an RBA0 backup is selected during restore or recovery processing, it causes a delete/define operation for the VSAM file.

Forward recovery with RBA0 backups

You can perform a forward recovery of a file across RBA0 backups. For more information about the actions that RUV takes during forward recovery if you are using the RBA0 backup detection feature, see Forward-recovery-and-the-RBA0-backup-detection-feature.

Identifying an RBA0 backup

When you are viewing information about backups with the RUV ISPF interface, RBA0 backups contain information similar to the following:

Implementing the RBA0 backup detection feature

To implement the RBA0 backup detection feature, use a RUV rule set to register the VSAM file and all programs that update the file:

• To register the file, code the ADD VSAM_FILE command or the ADD VSAM_GROUP_DEFINITION command.
• To register the programs that update the file, code the ADD JOB_SET command.

RUV must detect all updates against the file, especially the initial load. When a file is opened, RUV detects that the file is empty and records an RBA0 backup in the repository. A dummy record is then journaled to a RUV archive. CICS performs its own journaling operations as the file is updated. RUV detects these updates when the CICS log stream or extent is archived.

Normally, the initial load of a VSAM file is not journaled. The RUV rule set either excludes the name of the program that is performing the load or excludes the VSAM file data set name for the load job. Therefore, to enable the RBA0 detection feature, you must modify the rule set to include both the loading program name and the data set name of the VSAM file. If IDCAMS or another general-purpose utility is being used to process the file, use a job-level rule set to restrict RBA0 detection to selected files.

For complete information about constructing RUV rule sets, see Using-the-Batch-Journaling-Facility.