z/OS DFSMSdfp Advanced Services
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Reexecuting Channel Programs by Error Recovery Procedures

z/OS DFSMSdfp Advanced Services
SC23-6861-01

Under some circumstances the ERP might reexecute a channel program from the beginning. For example, DASD channel programs are almost always retried from the beginning. You will want to build channel programs that the ERP can restart after any CCW or DCW has failed.

For CCW channel programs, if a CCW modifies a data area used by an earlier CCW, the channel program might not reexecute properly.

The following are some situations where a channel program might not give correct results when reexecuted by the ERP (see Modifying a Channel Program During Execution):
  • The channel program modifies itself.
  • The application program or the PCI appendage modifies the channel program or a data area before receiving notification that the channel program has completed. Generally you can attempt to add CCWs to the end of the channel program.
Parent topic: Interruption Handling and Error Recovery Procedures

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