The following describes how to specify checkpoint data sets through the CKPTDEF initialization statement.

The CKPT1= specification is used for the primary data set copy of the JES2 checkpoint information, and the CKPT2= specification is used for either the DUPLEX data set copy (if operating in DUPLEX mode) or the second primary data set copy (if operating in DUAL mode). Before setting the DUPLEX=ON|OFF parameter for a particular member of your configuration, you should consider whether it is practical for your MAS to use an entire volume for the duplex data set.

If the checkpoint resides on DASD, prefix the checkpoint data set names with SYS1. to provide a complete data set name (for example, SYS1.JESCKPT1 and SYS1.JESCKPT2). Define the placement of these data sets using the VOLser subparameter of the CKPT1= and CKPT2= parameters on the CKPTDEF initialization statement.

If the checkpoint resides on a coupling facility structure, you do not specify a volume. In this information, checkpoints that reside on coupling facility structures are represented as SYS1_CKPT1 and SYS1_CKPT2. Either the CKPT1= or the CKPT2= parameter on the CKPTDEF initialization statement must be specified; there is no default for the data set name, the volume serial number, or the structure name. Proper placement is vital to JES2 performance, particularly in a multi-access spool configuration environment.

Providing security for JES2 discusses using RACF® to protect the checkpoint data sets that reside on DASD. Checkpoint data sets that reside on a coupling facility structure are RACF-protected by the coupling facility service.