Defining system access to pool and VIO storage groups

If you want a system to access a pool storage group, you must ensure that devices on which the groups reside are physically connected to the system.

No devices are associated with a VIO storage group. However, the SMS status associated with the VIO storage group determines if this storage group can be used by each system in the complex. The SMS statuses, described below, show the relationships between each system in the SMS complex and a given VIO or pool storage group.

DISALL

Disable All prevents the system from allocating or accessing data sets in the storage group.

DISNEW

Disable New prevents the system from allocating new data sets (and DISP=MOD data sets that do not currently exist) in the storage group. DISNEW prevents data sets from extending to a volume whose volume or storage group status is DISNEW.

ENABLE

The system can allocate and access data sets in the storage group. ENABLE is the default relationship between a system and a storage group.

NOTCON

Not Connected indicates that the storage group is defined but not accessible to the system. It resembles DISALL, except you cannot dynamically change the NOTCON system status for Storage Groups. You can, however, change it for volumes.

Use the VARY command to change the status of a volume from NOTCON to another status. If you want a storage group to have access to NOTCON volumes, physically connect them to the system, define the connection by changing the system status in the ISMF Storage Group Application, and activate the configuration that defines the connection. If you use the VARY command to change the status of a volume the change is made in the ACDS and not the SCDS, so the status will change to whatever is defined in the SCDS if an SCDS is subsequently activated.

QUIALL

Quiesce All prevents the system from scheduling jobs that allocate or access data sets in the storage group. This state only affects JES3 systems, that support job scheduling.

When the job is executing, QUIALL has the same effect in a JES2 or JES3 environment. In an JES2 environment, the volumes become a secondary volume selection candidate through QUIALL. Secondary volume selection candidacy means that these volumes are still available for allocation, but less preferred than other volumes.

For more information about primary and secondary volume selection candidacy, see Conventional volume selection.

QUINEW

Quiesce New prevents the system from scheduling jobs that allocate new data sets (and DISP=MOD data sets that do not currently exist) in the storage group.

If the system uses JES3 to schedule jobs, you can use QUINEW only as long as other volumes are available. Before scheduling a job, JES3 verifies that all resources are available, unlike JES2, which schedules a job even if all the needed resources are not available. This can lead to a contention for resources, because a job running under JES2 can hold some resources while it waits for others to become available. Under JES3, if any of the candidate volumes are available, JES3 schedules the job and SMS selects the volume. Under both JES2 and JES3, SMS selects QUINEW volumes only as a last resort.

For more information about primary and secondary volume selection candidacy, see Conventional volume selection.

Note: Because an extend storage group is a pool storage group, the SMS status also applies to the extend storage group.