Memorex MT2028D-BLK User Manual download pdf (Page 27)

Chapter 7: Detach Processing

The operational flexibility of the DYNVM extension is greatly dependent upon

Automatic Volume Recognition (AVR). Every AVR routine of DYNVM

dynamically attaches FREE tape drives to the respective AVR routine and reads

the VOL1 label in an attempt to verify the volume serial number. The tape

drive is then dynamically detached to allow AVR of the next tape drive or just

the tape drive if the proper tape volume is located, to be attached to the

requesting virtual machine.

CP, however, unconditionally unloads the tape drive during each detach

processing. This can cause operational problems because FREE tape volumes

will unload during every AVR scan.

The DETNOUNL option of the DYNVM system profile resolves such problems by

intercepting the DETACH command within CP. All DETNOUNL parameters are

described in detail in this chapter.

DETNOUNL Parameters

The DETNOUNL option intercepts DETACH commands within CP. It is provided

with three parameters:

VDEVBLOCK

Causes the VDEVBLOK to be altered by DYNVM before each DETACH

issued by the service machine.

This option requires that the DYNVM service machine have class C

Privileges. If this option is selected for a VM/XA system, it will be

dynamically changed to DETNOUNL RDEVBLOK upon initialization, and the

CADT774E message will be issued.

RDEVBLOCK

Causes the RDEVBLOK to be temporarily altered by DYNVM during DETACH

processing, ensuring that HCPDTD will not attempt an unload operation for

the specified device.

It requires that the DYNVM service machine have class C Privileges and is

valid only for VM/XA, VM/XA SP, VM/XA SF, VM/SEPP, VM/BSEPP, VM/HPO,

VM/SP, VM/ESA, or z/VM systems.

Chapter 7: Detach Processing 7–1

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Memorex MT2028D-BLK User Manual Page 27