The MAXDRIVES setting determines the number of tape drives that the Backstore Engine is allowed to use concurrently. The total number of tape drives in use is the actual count of devices allocated to Recall and Externalization tasks. These values can be displayed by issuing the SVTn Display Backstore console command for those CA Vtape subsystems that are executing Recall and Externalization tasks.
When MAXDRIVES is not set to zero, the Backstore Engine only applies the MAXDRIVES limit to Externalization tasks, not Recall tasks.
If starting a new Externalization task would cause the total number of drives in use to exceed the MAXDRIVES setting, the task is rescheduled. Recall tasks are always started, even if the number of drives in use will exceed the MAXDRIVES. This is done to minimize application wait time for a recall.
How the Backstore Engine reacts when the MAXDRIVES setting is exceeded is controlled by the setting for the FullMaxdrivesEnforcement attribute in the <DynamicOptions> Section of parmlib.
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