Restrictions of the QUICKSTART for MVS Checkpointing facility

The primary restrictions of the MVS Checkpoint Facility are:

• Even though the application program may have been changed, perhaps to correct an error within the program, the altered version of the program is not honored during a restart. The original application program object code is loaded into the address space by the MVS Checkpointing Facility. Therefore, if an application program error caused the ABEND, the application program is NOT restartable.
• The device types used for the application program's data sets must be the same during a restart as they were used during the initial execution of the job. There can be no switching from Disk to Tape, for example, or from 3380 Disks to 3390 Disks.
• If VIO data sets are used, they must be accessed using either BSAM or QSAM and must be redefined as DD DUMMY data sets during a restart.
• The REGION=parameter on the job Statement or on the EXEC Statement of the Step can be increased when the job is restarted, however it cannot be reduced to a smaller size than its setting at the time of the Last Checkpoint.
• All DD Statements which had existed at the time of the previous MVS Checkpoint must exist at the time of the restart.Additional DD Statements can be added, as needed.
• All DD Statements which had existed at the time of the previous MVS Checkpoint must have the same Extents, although additional capacity can be specified (on the same Volume by overriding the SPACE= sub-parameter during a restart.
• All datasets referenced in the Step JCL must reside on the same volumes during a restart as they did at the time of the last MVS Checkpoint. Additional volumes can be added, but only by overriding the DD Statement VOL= sub-parameter.
• VOL=REF cannot be used during a restart for the “current” Step or for anynsubsequent Step if they contain values for Step Name or StepName.ProcStepName,which refers to a Step preceding the restart Step.
• The DD Statement sub-parameters DISP, DCB, LABEL and UNIT cannot be changed during a restart.
•  An IPL of the operating system is tolerated between restarts, but modules that reside in the LPA that are executed during the application program's execution must be in the same storage location during a restart.
• The MVS nucleus cannot have changed between restarts.
• There is no support for nonstandard tape labels.

• The application program must be compiled with the NODYNAM option.

  Warning

  Note

  Certain types of VSAM access are stated to be restartable, but testing has shown that updating VSAM KSDSs is unreliable with respect to restartability.