Advanced Topics › Control and Checkpoint File Considerations › Create Checkpoint Files

Create Checkpoint Files

If you want to create a checkpoint file, you must create a separate file on each system. These are not shared files like DASD control files.

To create a checkpoint file

1. Customize and submit the sample JCL found in the ALLOCKPT member of the CAI.CBTDJCL data set.
2. Specify the MIMINIT CHKPTDSN statement in the MIMINIT member to define the LOCAL checkpoint file prefix, or define the specific checkpoint file data set names using ALLOCATE commands in the MIMINIT member.

The checkpoint file is especially important when you are using the CTCONLY or XCF communication method. We recommend you allocate a primary and an alternate checkpoint file on each system in the complex. A recovery migration to the alternate checkpoint file occurs if the primary file become unusable due to hardware error or file space shortage problems. We recommend that you allocate the alternate checkpoint file to a size slightly larger than the primary checkpoint file.

To define checkpoint file prefixes

You use multiple MIMINIT CHKPTDSN statements in the MIMINIT member to define checkpoint files. The following example illustrates a two-system complex in which you have allocated primary and alternate checkpoint file names:

MIM.SYSA.CKPT00     (primary)
MIM.SYSA.CKPT01     (alternate)
MIM.SYSB.CKPT00     (primary)
MIM.SYSB.CKPT01     (alternate)

You would define the preceding checkpoint files in a shared MIMINIT member as follows:

IF SYSA
  MIMINIT CHKPTDSN=MIM.SYSA.CKPT
ENDIF
IF SYSB
  MIMINIT CHKPTDSN=MIM.SYSB.CKPT
ENDIF

To define specific checkpoint files

As an alternative to defining checkpoint prefixes, you can use multiple ALLOCATE commands in the MIMINIT member, qualified by IF/ENDIF statements, to define specifically named checkpoint files. The following illustrates a two-system complex in which you have allocated primary and alternate checkpoint file names:

MIM.SYSA.PRIMCKPT (primary)
MIM.SYSA.ALTCKPT (alternate)
MIM.SYSB.PRIMCKPT (primary)
MIM.SYSB.ALTCKPT (alternate)

You would define the preceding checkpoint files in a shared MIMINIT member as follows:

IF SYSA
   ALLOCATE DDNAME=MIMCKP00 DSNAME=MIM.SYSA.PRIMCKPT
   ALLOCATE DDNAME=MIMCKP01 DSNAME=MIM.SYSA.ALTCKPT
ENDIF
IF SYSB
   ALLOCATE DDNAME=MIMCKP00 DSNAME=MIM.SYSB.PRIMCKPT
   ALLOCATE DDNAME=MIMCKP01 DSNAME=MIM.SYSB.ALTCKPT
ENDIF