4. FILES › 5.2 VTS Component Files › 5.2.2 VTS Component IVT Information Area Files › 5.2.2.3 VTC Statistics Detail File (IVTVTC) › 5.2.2.3.3 IVTVTC Usage Considerations

5.2.2.3.3 IVTVTC Usage Considerations

This section identifies any special considerations or
techniques related to using the IVTVTC file.

The IVTVTC file contains an observation for each virtual tape
controller associated with a peer-to-peer VTS configuration.

In a peer-to-peer VTS configuration, the virtual controllers
(up to eight) handle the virtual tape I/O reads and writes
between workloads on z/OS and the DASD cache of the
participating UI and Secondary VTSs.

An important function of a peer-to-peer VTS is making copies
of each virtual volume.  If a virtual volume is created in
the DASD cache of the UI VTS, a copy is made in the DASD
cache of the secondary VTS and the other way around.

In addition to managing the z/OS I/O, the virtual controllers
also manage the I/O associated with making copies of virtual
volumes in the DASD cache of the UI or secondary VTSs.

Data element Composite Library Association (IVTCMPID)
identifies the peer-to-peer composite VTS served by the
virtual tape controllers. VTS Composite Library Activity
(IVTVCL) file observations with the same IVTCMPID value
contain data elements summarizing the virtual tape controller
activity captured in the individual IVTVTC file observations.