The CA TLMS Volume Master File (VMF) is a BDAM file which can be accessed through programs TLMSVMRW and TLMSVMIO. The file contains multiple record types, with related records chained together. Volume records can be accessed by an internal index structure.
The Volume Master File consists of a 500-byte record for each volume in the tape library. The name, number, status and characteristics of each data set in the tape library are maintained in this file.
The VMF dimension is strictly related to the number of VOLUMEs and AUXILIARY RECORDS defined during its allocation. It is usually allocated as a single volume dataset but when it reaches the maximum single volume allocation of 64K tracks, due to new volumes and AUX records added, is it possible to have it extended as a multi-volume dataset?
As BDAM access method is used for VMF. this access method can not be used with DSNTYPE=LARGE datasets. For this reason a VMF can not be allocated as a DSNTYPE=LARGE dataset.
So, if it reaches the maximum single-volume allocation of 64K tracks and it needs to be expanded due to new Volumes and AUX Records added, it is possible to allocate it as a multi-volume dataset.
Here a sample allocation jcl that can be used to accomplish this:
//ALLMVMF JOB (.........................
//NEWVMF EXEC PGM=IEFBR14
//VMF DD DISP=(,CATLG),SPACE=(CYL,(4000,4000),,CONTIG),
Since TLMSVMRW uses standard IBM READ/WRITEs to the VMF, the normal CATVMFx utilities can be used to manage this multi-volume VMF.