DFSMSdfp: Configure clusters and storage groups for SMS volume selection
Description
Before z/OS V2R1, when allocating or extending a multi-volume data set, SMS preferred the candidate volumes in the same storage facility image (SFI) if the storage class accessibility attribute was set to CONTINUOUS or CONTINUOUS PREFERRED. With z/OS V2R1, SMS prefers volumes that are in the same cluster. Similarly, when allocating the target data set for the data set fast replication function, SMS now prefers volumes that are in the same cluster as the source data set. In both cases, if it is not possible to honor the preference of volumes in the cluster, SMS reverts to preferring volumes in the same SFI. If you wish SMS to select volumes in the same cluster, you should configure your clusters accordingly.
Before z/OS V2R1, when allocating a striped data set, SMS allocated the stripes across separate logical control units (LCUs). With z/OS V2R1, SMS attempts to allocate the stripes across separate extent pools. If this is not possible, SMS continues to allocate the stripes across LCUs. If you wish SMS to separate the stripes across extent pools, you should configure your storage groups accordingly.
Table 1 provides more details about this migration action. Use this information to plan your changes to the system.
| Element or feature: | DFSMSdfp. |
|---|---|
| When change was introduced: | z/OS V2R1. |
| Applies to migration from: | z/OS V1R13. |
| Timing: | After the first IPL of z/OS V2R2. |
| Is the migration action required? | No, but recommended for optimum efficiency of data set fast replication and for the most uniform performance with striped data sets. |
| Target system hardware requirements: | None. |
| Target system software requirements: | None. |
| Other system (coexistence or fallback) requirements: | None. |
| Restrictions: | None. |
| System impacts: | None. |
| Related IBM Health Checker for z/OS check: | None. |
Steps to take
If you wish SMS to select volumes in the same cluster, configure your clusters accordingly.
For striped data sets, if you wish SMS to separate the stripes across extent pools, configure your storage groups accordingly.
Reference information
For more information about SMS volume selection and about striped data sets, see z/OS DFSMSdfp Storage Administration.