A pool is a group of rack numbers or volumes
that share a common prefix.
In DFSMSrmm, there are two
categories of pools: rack and scratch.
A
rack pool is shelf space that can be
assigned to hold any volumes. Although you can add scratch volumes
to these pools, you cannot normally use these volumes to satisfy non-specific
mount requests. A rack pool cannot be used with the DFSMSrmm system-based
scratch pooling. Rack pools can perform these functions:
- Hold volumes that are temporarily brought into the library but
will be returned to the owner after a period of time
- Hold customer, foreign tapes, and software product volumes
- Contain scratch volumes for use with DFSMSrmm exit-selected scratch
pooling
A scratch pool is shelf space assigned
to hold volumes for use with the DFSMSrmm system-based scratch pooling.
The volumes assigned to this shelf space can be used to satisfy scratch
requests as long as the volumes are in scratch status. Once the volume
has been written to, it becomes a volume with MASTER status, until
the volume is returned to scratch status. The volume remains in the
same DFSMSrmm system based scratch pool, in that it occupies the same
shelf space regardless of status.
The scratch volumes in a system-managed tape library can be from
one or more pools. DFSMSrmm does not provide pool selection or validation
for volumes in an automated tape library because ACS routines use
storage class and storage group to make allocation decisions, and
the library manager picks a scratch volume. DFSMSrmm provides pool
validation for volumes that reside in a manual tape library. You can
pool by storage group, exit-selected pool prefix, or DFSMSrmm system-based
pooling when using manual tape libraries.
DFSMSrmm allows you to use these basic types of pooling:
- Pools of shelf space that are based on rack number prefixes. Each
range identifies characteristics like management criteria and media
name. Use shelf space pools to store volumes that do not match your
installation-selected volume ranges and to store duplicate volumes.
Define shelf space pools by using the DFSMSrmm EDGRMMxx VLPOOL
command that is described in Defining pools: VLPOOL.
- Pools of volumes that are based on the volume serial number prefix.
These volumes do not have a rack number or the rack number matches
the volume serial number. Each range identifies characteristics like
management criteria and media name. Define volume prefix pools by
using the DFSMSrmm EDGRMMxx VLPOOL command that is described
in Defining pools: VLPOOL.
- Scratch pools. These can be one or more pools of volumes. Scratch
pools can be based on name, SMS storage group, prefix, or system.
You define scratch pools by using the SYSID, PREFIX, and NAME operands
of the DFSMSrmm EDGRMMxx VLPOOL command that is described
in Defining pools: VLPOOL.
- Storage groups. When you pool by storage group and use SMS ACS
processing to assign a storage group to a tape data set, or the volume
is in a system-managed manual tape library, DFSMSrmm ensures that
a volume from the correct storage group is mounted. The storage group
can be the same across multiple VLPOOL entries. You can use storage
group for scratch pooling for system-managed manual tape libraries
and non-system managed tape. Volumes that have been assigned storage
group names cannot be used to satisfy scratch mount requests that
do not request volumes from a specific storage group unless the mount
request is in a manual system-managed tape library.
Pools can be used in these ways:
- Adding shelf space - DFSMSrmm matches the rack number prefix to
the most specific VLPOOL prefix. The rack media name is taken from
the matching VLPOOL entry.
- Adding volumes - You can optionally specify RACK or POOL operands
to override default processing. Default processing matches the volume
serial number prefix to the most specific VLPOOL prefix. If a rack
number is found that matches the volume serial number and the specified
media name, the volume is stored in the matching shelf pool. If no
rack number is found, the volume is in a volume pool. When adding
a volume you can specify a storage group name so that the volume
can be in a specific scratch pool. If no storage group is specified
by the command, DFSMSrmm checks to see if the matching VLPOOL NAME
is a storage group, and uses that value as the storage group name.
In this case, the scratch pool matches the volume pool.
- Managing access to a volume - For system-managed tapes in a manual
tape library, DFSMSrmm validates the mounted volume for the requested
pool. You can use the installation exit to ignore the storage group
pool and use DFSMSrmm system-based scratch pooling described in Using storage group for manual tape library pooling.
- Defining actions that should be taken when volumes are ready for
release - You can define release actions for volumes on the pool level
that might not already be set for individual volumes. For example,
you can set the NOTIFY options so that DFSMSrmm sets notification
on the release action if it is not already on at the volume level.
- Selecting scratch pools for new tape data sets - For system-managed
tape, SMS ACS processing assigns a storage group. DFSMSrmm uses the
storage group name to pool the volumes into a scratch pool. For
non-system managed tape, DFSMSrmm calls SMS ACS processing to allow
a storage group to be assigned. If no storage group is assigned, the
EDG_EXIT100 installation exit is used.
When you pool by pool prefix, selected by EDG_EXIT100 or by SYSID,
and the VLPOOL prefix has an associated NAME, DFSMSrmm uses the pool
name for mount messages and drive displays but always validates mounted
volumes by using the pool prefix and SYSID. Multiple VLPOOL entries
can have the same SYSID values and the same NAME values.