What CA Dynam/T for z/VSE options need to be coded when sharing Tape Drives between two LPARS

Document ID : KB000011947
Last Modified Date : 14/02/2018
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Question:

What CA Dynam/T for z/VSE options need to be coded when sharing Tape Drives between two LPARS. We have AVRLCK=YES and wonder why. Is there any impact changing it to 'NO', additional to drives management ?

Answer:

The only thing that MULTCPU=YES does is prevent an open tape from being reused. If during AVR output processing a tape is AVRed that is in open status (as opposed to scratch status) and it normally would be allowed to be reused it won't be if MULCPU=YES is specified. 

The AVRLCK=YES indicates that AVR locking is to take place.

If drives are defined as different CUU's on different LPARS/CPU's than a DTLOCK macro must be coded. If AVRLCK=NO is specified the DTLOCK specifications are ignored.

AVRLCK=YES only pertains to tape drive sharing. <=== Catalog and Audit sharing have nothing to do with tape drive sharing/locking. 

If AVRLCK=YES is specified the drives are locked during AVR processing, and DT command processing i.e. STATUS and MTC commands.

If AVRLCK=NO is specified the “CUSTOMER” must be sure that the drives will never be able to be accessed from "TWO" LPARS at the same time. Otherwise problems can arise like the following: DT command crossed LPARS. They can access drives that are being used by other LPAR.

Resolution to prevent this: Customer to turn AVRLOCK on. 

 

Conclusion: to be on the safe side AVRLCK=YES should be specified when sharing Tape drives between two LPARS.