Mainframe Enablers TimeFinder SnapVX and zDP 8.5 Product Guide

Before you define groups, you must define the group dataset. The group dataset can be a partitioned dataset (PDS) or a partitioned dataset extended (PDS/E).

The group dataset must have the following characteristics:

RECFM=FB

LRECL=80

BLKSIZE=8880 (Or any valid multiple of 80)

The required amount of space is entirely dependent on expected usage. Secondary space is not recommended.

Two members are maintained for each group:

• The first member to hold the syntax
• The second member to hold the status and history

Use one directory block for every three groups. If the dataset fills, allocate a new dataset and copy all members from the old dataset into the new dataset.

You can specify the group dataset in three ways:

• Use the GROUP_DATaset_name parameter of the GLOBAL command.
• Use the DD statement //EMCGROUP DD to indicate the group dataset. You can concatenate multiple datasets together with EMCGROUP.
• Specify the &GROUP_DSNAME site option in the EMCSNAPO site options table.

Each group stores two members into the group dataset. One member contains the syntax or source statements. The other member contains the group description and history.

One member is all uppercase letters, and the other member is lowercase letters. The uppercase member contains the group history. The lowercase member contains the group syntax.

Each member has a cyclic redundancy check (CRC) calculated. If the CRC does not match, the group is unusable. This process prevents the members from being directly changed without the status also being updated.

The following example allocates a group dataset:

//IEFBR14  EXEC    PGM=IEFBR14
//GROUP    DD      DSN=group.dataset.name,DISP=(NEW,CATLG),  
//                 UNIT=3390,SPACE=(CYL,(3,3,90)),VOL=SER=volser,
//                 DCB=(RECFM=FB,LRECL=80,BLKSIZE=0)