ACS routines automatically determine SMS classes and storage groups for all new data set allocations and for data set allocations that occur from converting, copying, recalling, restoring, or moving data sets.

ACS routines determine the storage group when storing objects; or storage class and management class, when storing or changing objects.

The storage administrator writes ACS routines in the ACS programming language, one routine for each type of SMS class and one for your storage groups. These four routines, used together with the data class, storage class, management class, and storage group definitions, and the base configuration, define the SMS configuration for your site. The storage administrator stores the information on this configuration in a source control data set (SCDS). ACS routines do not apply to copy pools or aggregate groups. For more information, see SMS Configurations.

After writing the ACS routines, the storage administrator must translate them into an object form that SMS understands. A successful translation places the ACS object in a specified SCDS. After you activate the configuration contained in that SCDS, all new data set allocations use the ACS routines. You can test ACS routines in batch through NaviQuest or ISMF. For more information, see NaviQuest Tool for Batch.

Figure 1 shows a portion of a sample storage group ACS routine used to assign large data sets to the LARGE storage group and assign all other data sets to the PRIMARY storage group. Individual installations can determine their own standards for classifying data sets according to size. In Figure 1, data sets greater than 200␠000 KB are classified as large data sets; data sets smaller than those are placed in the primary storage group.

Figure 1. Example of a storage group automatic class selection routine

For example, you can implement the tape mount management methodology, using ACS routines to redirect small tape allocations to a pool storage group on DASD. DFSMShsm can automatically move the data sets together to tape at a later time and compact them. This methodology improves tape usage and significantly reduces tape mounts.

Related reading: For more information on using ACS routines, see z/OS DFSMSdfp Storage Administration.