The VMTAPE LIST SCRATCH command uses the PICK file indexes on the VMTAPE 191 to produce its output. These PICK files are updated dynamically on the VMTAPE server for tapes that are used on that system.
However, when the TMC is shared by 1 or more other systems, these PICK files do not reflect tape usage for the other systems that also use the TMC.
Therefore, when the TMC is shared, you need to periodically run the VMTAPE REFRESH command on each VM:Tape server. The REFRESH command causes VMTAPE to read the TMC to update its (local) PICK files, thus incorporating any tape status changes from all systems that share the TMC. How often you run VMTAPE REFRESH depends on your frequency of tape usage and/or how important the output from VMTAPE LIST SCRATCH is for your site.
Regardless, when VMTAPE selects a SCRATCH tape by using its PICK files, the selected volume is always validated against the TMC to verify the tape is still in fact SCRATCH. If some other system has used/saved the tape, VMTAPE will select another SCRATCH tape … the final verdict for SCRATCH tape selection is always the real-time status of the tape in the TMC.
To verify the “real-time” status of a tape in the TMC (bypass the PICK files), you can use the … VMTAPE QUERY VOLUME _volser_ DETAILS … command. This command gets the status of the volume by reading the TMC.