You control the use of the checkpoint data set by specifying parameters on the $T MASDEF and $T CKPTDEF commands. The $T MASDEF command allows you to specify MAS definition and tuning parameters. You can specify the minimum and maximum time a MAS member must wait to regain control of the checkpoint data set, how long that member can have control, and at what time interval JES2 determines that a lockout condition exists. You can also specify whether direct access volumes should be marked “shared” or “non-shared”, and at what time interval JES2 assumes that a MAS member is inoperative.

You can use the $T CKPTDEF command to specify the checkpoint definition and to initiate a checkpoint reconfiguration dialog with JES2. Specify ON or OFF on the DUPLEX parameter to tell JES2 whether CKPT2 is used as a backup of the CKPT1 data set. You may specify that alternate data sets be used in place of the CKPT1 and CKPT2 data sets. The RECONFIG=Y parameter puts JES2 in a dialog so that you can supply the information necessary to reconfigure the checkpoint data set specifications.

z/OS JES2 Initialization and Tuning Guide, SA32-0991 provides several examples of JES2- and operator-initiated checkpoint failure and recovery procedures. It is highly recommended that you familiarize yourself with these dialogs and procedures before attempting to reconfigure the checkpoint environment.