The Backstore Engine › Configuring the Backstore Engine in Primary and Failover Roles

Configuring the Backstore Engine in Primary and Failover Roles

Based on the values set for some parmlib attributes and settings, a Backstore Engine can be defined as a Primary Server for all Externalization and Recall activities or a Failover Server. We recommend this configuration to minimize the number of tapes, and physical tape drives being used.

The Primary Server will take care of all Externalization and Recall tasks for a CA Vtape Complex installed on one or more LPARs. The Failover Servers will be dormant, waiting to take over this work if needed. With this configuration, you can centrally manage the Externalization and Recall processes from just one LPAR and CA Vtape subsystem without having to track tasks, alerts, commands, and messages from multiple LPARs and subsystems.

The configuration of Primary and Failover Servers in a CA Vtape Complex is very simple. All the CA Vtape Subsystems in the same CA Vtape Complex should share the same Group Definitions and the same Externalization and Recall related attributes in the <DynamicOptions> section of parmlib. All subsystems should also have FullMaxdrivesEnforcement set to a value of Y. These parmlib attributes are:

• CacheAutoHoldLowThreshold
• CacheAutomationSchedule
• CacheAutoReleaseHighThreshold
• CacheWarningThreshold
• FullMaxdrivesEnforcement (must be set to Y)
• RecallNotificationEvent
• RecallServer (must be set to SERVER)
• RecallServerTimeout

Setting these parmlib attributes to the same values will ensure that each Backstore Engine reacts in the exact same way once MAXDRIVES is set to a value greater than zero.

A Backstore Engine is the Primary Server when its MAXDRIVES is set to a number greater than zero. A Backstore Engine is a Failover Server when its MAXDRIVES is set to zero. To accomplish this the SVTn SET MAXDRIVES=0 console command is issued for the CA Vtape Subsystems that are the Failover Servers and SVTn SET MAXDRIVES=nn where nn is a value greater than zero for the CA Vtape Subsystem that is the Primary Server.

The Startup Commands Section and the Shutdown Commands Section in the CA Vtape parmlib or your own automation product can be used to automate the issuing of these commands for the Primary and Failover Servers.

When a problem occurs that prevents the Primary Server from processing Recall or Externalization requests, issuing the SVTn SET MAXDRIVES=nn console command for one of the Failover Servers will make it the Primary Server. If the original Primary Server should not perform any physical tape mounts until the problem is resolved, its MAXDRIVES setting should be changed to zero.