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Interactions Between the Task Level and Global Exits z/OS DFSMSdfp Advanced Services SC23-6861-01 |
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If both task level and global DESERV exits have been defined, there is a prescribed calling sequence. The task level exit is called first. If the task level exit indicates that the DESERV function should be terminated (via a return code 4 from the exit), DESERV returns immediately to its caller. However, the global exit is given control when the task level exit returned with return code 0. The global exit can indicate (via return code 4) that control should pass back immediately to the DESERV caller. In this case before returning to the DESERV caller, the task level exit is given control indicating that the DESERV function is complete. After returning from the task level exit, DESERV returns to the caller. If the global exit returns with return code 0, the DESERV function executes, making the post-processing exit calls. The post processing exit calls are made first to the global exit and second to the task level processing exit. This sequence (the reverse of the pre-processing exit sequence) is chosen to simulate the return sequence that would have been seen if both SVC screen routine and updated SVC routine were in place. The following diagram illustrates the exit routine call sequence: Figure 1. Exit Routine Call Sequence
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