Setting up scratch pools for BTLS-managed volumes

Defining pools: VLPOOL provides information on defining VLPOOL and other EDGRMMxx options.

Both DFRMM and DFSMSrmm use VLPOOL scratch pool definitions to perform these functions:

Update mount messages.
Update 3480 and 3490 drive displays if the MSGDISP installation exit IGXMSGEX is called.
Reject scratch volumes that are not from the correct pools.

If you plan to use DFSMSrmm with BTLS, you must define and use scratch pools with special care to prevent DFSMSrmm from rejecting volumes needlessly. DFSMSrmm does not know that volumes managed by BTLS reside in an automated tape library and attempts to control scratch tape assignment for mounts inside the automated tape library. DFSMSrmm, on the other hand, does not attempt to control scratch tape assignment for mounts inside a system-managed automated tape library.

If you have scratch volumes that reside in an automated tape library managed by BTLS, define pool definitions to include all the volumes that you want to use. DFSMSrmm accepts or rejects volumes that are based on the VLPOOL definitions that you provide in parmlib member, EDGRMMxx. For volumes that reside in an automated tape library and are managed by BTLS, ensure that the VLPOOL definitions do not cause conflicts when scratch volumes are used.

For example, consider these VLPOOL definitions:

VLPOOL PREFIX(A*) SYSID(A) TYPE(S)
VLPOOL PREFIX(B*) SYSID(B) TYPE(S)

On system A when a scratch volume is requested, if the automated tape library contains volumes from both pools A* and B*, it can select a scratch volume from either pool. If the Library Manager selects a volume in pool B*, DFSMSrmm rejects it. The Library Manager might never select a volume that can be used because all available scratch volumes are selected until a volume that is acceptable to DFSMSrmm is found.

If you want DFSMSrmm to manage pool selection when using BTLS, use the NAME operand on the VLPOOL definition for the pool to specify a pool name. For example, you could define VLPOOL definitions as follows:

VLPOOL PREFIX(A*) NAME(SCRTCH5) TYPE(S) SYSID(SY1) DESC('BTLS pool 5')
VLPOOL PREFIX(B*) NAME(SCRTCH3) TYPE(R) DESC('BTLS pool 3')

DFSMSrmm uses the value in the NAME operand to update messages and tape drive displays for non-specific mount requests. Do not use the NAME operand if your operations depend on a pool prefix rather than a pool name.

For scratch pools of volumes that are contained in an automated tape library that are managed by BTLS, use the NAME operand when specifying the SYSID operand on VLPOOL definitions. For more information, refer to Returning BTLS-managed volumes to scratch.