4. FILES › 5.2 VTS Component Files › 5.2.3 VTS Component SVT Information Area Files › 5.2.3.4 Virtual Tape Volume Mount Request File(SVTVMR) › 5.2.3.4.3 SVTVMR Usage Considerations

5.2.3.4.3 SVTVMR Usage Considerations

A primary performance goal for virtual tape subsystems is to
satisfy virtual tape accesses in the disk buffer.  When
virtual tapes must be recalled from physical tape cartridges,
performance suffers dramatically.  While totally eliminating
virtual volume recalls is impossible, recalls should be
minimized.

Data in the SVTVMR file can provide insight to assist the
storage administrator in adjusting management classes to
either keep virtual volumes in the disk buffer longer, or to
predict when volumes might be needed; thus forcing them to be
recalled in advance so they are resident in the disk buffer
when required.  Any improvement in minimizing virtual volume
recalls increases virtual tape subsystem throughput.