Both checkpoints on DASD

Placing both checkpoints on DASD volumes reduces throughput of data and can lock out smaller MAS members from access to the checkpoint. For information on tuning checkpoints residing on DASD, see Controlling the size of the change log and Controlled checkpoint data set access.

For further information concerning specification of checkpoint data sets, see the CKPT1= and CKPT2= initialization parameter descriptions on the CKPTDEF statement in z/OS JES2 Initialization and Tuning Reference.

Attention: IBM® does not recommend placing both checkpoints on coupling facility structures or placing the primary checkpoint on DASD and the secondary checkpoint on a coupling facility structure. If both checkpoints reside on Coupling facilities that become volatile (a condition where, if power to the coupling facility device is lost, the data is lost), your data is less secure than when a checkpoint data set resides on DASD. If no other active MAS member exists, you can lose all checkpoint data and require a JES2 cold start. Placing the primary checkpoint on DASD while the secondary checkpoint resides on a coupling facility provides no benefit to an installation.

Note: All combinations of checkpoint data sets on DASD and coupling facility structures are supported as potential error recovery scenarios through the checkpoint reconfiguration dialog.