Processing System Level Backup (SLB) image copies

IMS Database Recovery Facility Extended Functions has the capability to use IMS Recovery Expert System Level Backups (SLB) as recovery assets.

When IMS Recovery Expert creates an SLB, it can keep track of all database data sets (DBDS) that are backed up in the SLB. The SLB contains the equivalent of fast replication image copies for each DBDS in the SLB.

A dynamic application programing interface (API) is provided that allows Extended Functions jobs to utilize these SLBs for image copies when those SLBs can meet the recovery criteria better than an image copy recorded in the RECON data sets. By using IMS Recovery Expert SLBs as image copies, you can reduce the need for creating image copies.

Setting up the environment to use SLB image copies

The IMS Recovery Expert SLB API allows Extended Functions jobs to use SLBs as image copies. The API requires information relating to the IMS Recovery Expert environment. This information includes the names of the IMS Recovery Expert repository data sets and the execution load libraries.

This information is provided in one of two ways:

  • Modify the Extended Functions JCL to include DD statements for each of these data sets, or
  • Run the SLB API utility to dynamically build the API environment that allows Extended Functions jobs to access the required information without the need for JCL changes.

The recommended method is to use the dynamic SLB API activation utility so that Extended Functions JCL does not have to be changed.

The dynamic API activation utility is discussed in the following topic:

Setting up the environment to support SLB image copies

Controlling the use of SLBs

The use of IMS Recovery Expert SLBs by Extended Functions jobs is controlled by the USESLBIC() keyword.

  • When USESLBIC(Y) is specified, Extended Functions jobs use the SLB API and SLBs can be used as sources for image copies.
  • When USESLBIC(N) is specified, SLBs are not used.
  • When USESLBIC(Y) is set, and a given database is not contained in the SLB used for processing the recovery list, Extended Functions attempts to use non-SLB image copies as sources for image copies.

    These image copies must have time stamps greater-than or equal-to the time stamp of the SLB.

When Extended Functions jobs run with USESLBIC(Y) and determine that there is an SLB that best matches the recovery criteria, the SLB API issues a NOTIFY.IC command to create an image copy record in the RECON data sets for that SLB image copy.

The format of the SLB image copy record data set name is:

SLB.Ixxxx.Dxxxx.dbdname.ddname

The SLB image copy data set name is symbolic and no physical data set exists with that name. When:

  • An SLB image copy record exists in the RECON data sets, and
  • An Extended Functions job is run with USESLBIC(N), and
  • The job determines that this record should be used for recovery,
  • then the job fails when attempting to allocate the symbolic data set.

Therefore, once Extended Functions jobs execute with USESLBIC(Y), the jobs should continue to run with this setting.

Using SLBs as recovery assets

When USESLBIC(Y) is specified, Extended Functions is able to use SLBs as recovery assets:

  • SLBs are created by IMS Recovery Expert and written to fast-replication devices.
  • SLBs can also be offloaded to other DASD or tape devices. Therefore SLBs can exist on fast-replication devices, offload data sets, or both.
  • If the SLB exists on both, the SLB on the fast-replication device is used in recovery.

If there are offload data set(s), they are displayed on the VERIFY(ALLOC) and VERIFY(OPEN) reports. This does not necessarily indicate that the offload data set(s) are used for recovery. It just indicates that they are available if needed. If the offload data set(s) are used, the recovery report indicates that fact.

When an SLB is used for recovery, the SLB API issues a NOTIFY.IC to register the image copy record in the RECON data sets. These image copy records are the symbolic records discussed earlier. IMS Recovery Expert can be used to delete the SLB from the fast replication devices.

As long as the SLB still exists on offload data sets, the SLB, and any symbolic image copy records associated with the SLB, are still usable. However, if the offload data sets are also deleted, the symbolic image copy records are no longer valid. If you want to ensure that these records are not used, you can delete them from the RECON data sets.

The VERIFY function can be used to determine the correlation between the SLB's fast-replication volume(s) and the offload data sets.

When USESLBIC(Y) is specified, and either databases are being recovered or their recovery assets are being verified, it is a best practice to examine the job log for FRD4312E and FRD4320I error messages.

These messages are displayed when there is an error in the application programming interface between IMS Database Recovery Facility Extended Functions and IMS Recovery Expert or when the database is not contained in the SLB.