Using the Basic Components › Recall Sources

Recall Sources

The Backstore Engine can stack the Virtual Volumes on a Primary tape, a Duplex tape, and a Triplex Unix System Services (USS) File System. When the Peer-To-Peer Option is licensed and configured, the Remote Backstore Engine can create the same copies. All of these Backstore Copies of Virtual Volumes are Recall Sources, copies of the Virtual Volumes that can be used by a Recall Server.

When running with Dynamic Cache Management, CA Vtape maintains counters for Recall Sources, and establishes a hierarchy for automatically moving through these sources should a recall attempt fail. Recall works in conjunction with the SET RECALL command, and the RecallAttemptsThreshold and OffsiteBackstoreCopy definitions to determine when a Recall Source change should occur and what Recall Sources are eligible.

RecallAttemptsThreshold limits the number of times a Recall is attempted from any one Recall Source. Once the threshold is exceeded, if another Recall Source is available, Recall will attempt to use it. Once all Recall Sources have exceeded the threshold, the Virtual Volume will be mounted as an empty volume and the application will take an sx13 ABEND.

OffsiteBackstoreCopy determines if any Recall Source should be excluded from Recall processing. A RecalI Source that has been sent off-site and vaulted can be excluded from Recall processing.

Setting or defaulting RecallAttemptsThreshold to zero disables this feature and Recall will always use the Backstore copy specified by the SVTn SET RECALL console command or the default of Primary, after applying the OffsiteBackstoreCopy exclusion rule.

Each time a recall is required, the user catalog defined for CA Vtape data sets is interrogated for Backstore Copies.

To minimize network traffic, local Recall Sources are always preferred over remote Recall Sources (Peer-To-Peer).