If end-of-volume is encountered during writing of a checkpoint entry, a second attempt is made to create the checkpoint entry on another volume if another volume has been allocated. If the checkpoint data set extends during writing of a checkpoint entry, a second attempt is made to create the checkpoint entry by writing over the first attempt and using the new extents. If EOV occurs or the data set extends before the second attempt at writing the entry is completed, message IHJ0001 (invalid checkpoint) is issued. Control is returned to you with a X'08' return code in register 15 and a reason code of 27 in register 0.

The status (opened or closed) and position of a checkpoint data set remain the same at restart as they were after execution of the CHKPT macro instruction that established the checkpoint.

The first time a checkpoint data set is opened, checkpoint routines cause the OPEN macro to request security information for the data set from the operator.

Note: A checkpoint data set must contain only checkpoint entries. If a program attempts to write its own data in a checkpoint data set, message IEC954I will be issued, followed by an abend code of 23F.