TMC fields BLKSIZE and BLKCNT not populated

Document ID : KB000044008
Last Modified Date : 14/02/2018
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Introduction: 

VM:Tape TMC fields BLKSIZE and BLKCNT.

 

Question: 

TMC fields BLKSIZE and BLKCNT are not populated for tapes created on z/VM by VM:Backup, HiDRO and VM:Archiver.

These fields have a value of zero.  Is it possible to enable the fields to be populated? 

 

Environment:  

Tapes created by VM:Backup, HiDRO and VM:Archiver. 

 

Answer: 

VM:Backup, HiDRO and VM:Archiver do not populate the BLKCNT and BLKSIZE fields when they write data to tapes managed by VM:Tape. Those fields do get populated in z/OS though.   No matter what type of TMC it is, CMS does not provide facilities for capturing block counts, block sizes and VM:Tape does not maintain them.


Additional Information:

You may want to consider implementing VM:Tape's USERACNT user exit which is called by the MOUNT command and will initialize or modify local site-defined fields in the accounting area of the TMC record.  The accounting area is field ACCT and is 50 bytes long. .