Disaster alternate volumes

DFSMShsm provides a way—once you have created alternate tapes or have duplexed alternate tapes—to use those alternates in place of the original tapes for doing recalls or recovers.

If an actual disaster happens at your home site or if you are running a disaster recovery test, you should proceed as follows to establish operations at your recovery site:

1. Bring up the system by restoring the system packs, libraries, and DFSMShsm CDSs.
2. If your strategy includes dump tapes, set the DEFINE command at the recovery site to limit DFSMShsm recovery to those dump classes that are present there. It is likely that the CDS indicates the dump classes at the recovery site are those available at the home site.
3. Start DFSMShsm, and restore the required data sets from DASD.
4. If you have created alternate copies of DFSMShsm-owned tape volumes and the alternate volumes are present at the recovery site, run the TAPEREPL command to convert all of DFSMShsm’s information about the original volume serial number to the alternate volume serial number. Since this process is very time-consuming, a significantly reduced form of the TAPEREPL command can be run during the earliest stages of bringing up a recovery site. This command consists of TAPEREPL, followed by required parameters, followed by DISASTERALTERNATEVOLUMES, abbreviated to DAVOLUMES. For example:

   TAPEREPL ALL DAVOLUMES

   When the DAVOLUMES parameter is used, only base OCDS TTOC records of ML2 and backup tapes that have alternate volumes are updated as having disaster alternate volumes.

   The designation of disaster alternate volumes can help distinguish between alternate volumes initially present at the recovery site, and alternate volumes created later at the recovery site.

   Note: When the DAVOLUMES option is used, DFSMShsm does not invoke the tape-volume exit ARCTVEXT, since the original tape is not being totally replaced. For example, if this is done for a disaster recovery test, the resulting control data sets may be discarded after the test, and the original tapes again used at the home site.

   DFSMShsm invokes ARCTVEXT when the complete replacement is done, using TAPEREPL without the DAVOLUMES option.

5. Before running customer jobs, issue the SETSYS command with the DISASTERMODE parameter. For example:

   SETSYS DISASTERMODE

   One approach would be to put the SETSYS DISASTERMODE command in a startup ARCCMDxx PARMLIB member that is used exclusively for starting DFSMShsm in disaster mode.

   While DFSMShsm is running in disaster mode, recalls and recovers from tape volumes that are marked as having disaster alternate volumes will substitute the volume serial number of the disaster alternate volume from the TTOC record for the original volume serial number that appears in the data set records.

6. If you use TAPEDELETION(HSMTAPE) or PARTIALTAPE(REUSE) options then the inventory will likely contain empty and partially filled backup and migration tapes that were destroyed at the home site. These tapes will be selected for output at the recovery site. To prevent DFSMShsm from requesting tapes that are not available, identify these tapes using the LIST TTOC SELECT(NOTFULL) command, then mark the tapes full with the MARKFULL option of the DELVOL command:

   DELVOL volser BACKUP(MARKFULL)
   DELVOL volser MIGRATION(MARKFULL)

7. As jobs run at the recovery site and new data sets are created, backup versions and migration copies are created. As tapes are filled, they may be copied. These “new” alternate copies are not considered “disaster alternate volumes” and will not be substituted for the original volumes during recall or recover.
8. If you have finished running a disaster recovery test or you are finished using the alternates, reset the Disaster Alternate Volume flag in the TTOCs by issuing the following command:

   TAPEREPL ONLYDISASTERALTERNATES(RESET)

   If you were performing a disaster recovery test, you may want to make scratch tapes out of any DFSMShsm output tapes created at the recovery site. You may leave the alternate volumes for future disaster recovery.

9. If you are recovering from a true disaster, you now need to plan for the return to your home site. You need to convert the disaster alternate volumes to original volumes. You can issue:

   TAPEREPL ONLYDISASTERALTERNATES

   to replace all, and only, those original volumes identified as having disaster alternate volumes. The command HOLD TAPEREPL may be used if the TAPEREPL command needs to be stopped.
10. You can also replace specific original volumes with their disaster alternates. First, issue

    LIST TTOC SELECT(DISASTERALTERNATEVOLUMES)

    to identify those tape volumes with disaster alternate volumes, and then issue the TAPEREPL command without the DAVOLUMES parameter. For example, the command:

       TAPEREPL OVOLS(TKS001,TKS002,TKS003)

    where TKS001, TKS002, and TKS003 are volume serial numbers that were among those returned from the LIST TTOC command—will replace these specific original volumes with their disaster alternates.

    These newly converted original tapes need to be copied now for future disaster recovery.