Defining Data Classes

Use the results of your tape mount management analysis to help determine the sizes of the tape data sets that you direct to DASD. You can create several data classes to correctly allocate space for these data sets and develop ACS filter lists to help assign the proper data classes to the data sets. You can also have the user code the proper data class on the JCL DD statement. Many tape allocations do not specify the SPACE parameter, which is required when allocating data sets on DASD. You should plan to specify space parameters in your tape mount management data classes. This avoids situations where SPACE is not specified and a tape data set allocation is rerouted to DASD, causing the allocation to fail.

Using the Partial Release management class attribute can reduce the number of data classes needed to allocate space for tape mount management candidates. The CI option, release-on-close, releases allocated but unused space when the data set is closed or during the next space management cycle.

The following sample data classes are defined for use with tape mount management data sets:

TAPOSITE

Assigned to data sets that are usually stored offsite, such as vital records, disaster recovery backups, archives, and interchange data.

These tape data sets are allocated directly to tape.

TAPACTV

Assigned to active data sets larger than 600 MB. These data sets are allocated directly to tape.

TAPBKUP

Assigned to backup data sets, such as volume dumps and database image copies, that are larger than 600 MB. These data sets are allocated directly to tape.

TAPTEMP

Assigned to system-generated temporary data sets that are larger than 600 MB. These data sets are allocated directly to tape.

TMMACTV

Assigned to active data sets that are generally not LARGE. This data can be directed to the DASD buffer storage group as multivolume data sets (up to 10 volumes maximum).

These data sets are not usually allocated with a space request.

Data assigned to TMMACTV that contains no space information has a 200 MB primary allocation and a 20 MB secondary allocation.

TMMBKUP

Assigned to backup tape data sets that are generally not LARGE. This data can be directed to the DASD buffer storage group.

These data sets are not usually allocated with a space request.

Data assigned to TMMBKUP that does not contain space information has a 200 MB primary allocation and a 20 MB secondary allocation.

TMMTEMP

Assigned to system-generated, temporary tape data sets that are generally not LARGE. Data assigned to TMMTEMP that contains no space information has a 200 MB primary allocation and a 20 MB secondary allocation.

NONTMM

Assigned to data sets that should go to tape directly in a non-compacted form. This data is not intended for tape mount management. Only storage administrators and system programmers can assign this class.