Modifying the IOB Chain

This procedure is not recommended. However, to change the order in which purged I/O requests are restored or prevent a purged request from being restored, you can change the sequence of IOBs in the IOB chain or remove an IOB from the chain. The address of the IOB chain can be obtained from the purge I/O restore list (see Figure 1).(The address of the purge I/O restore list is shown at bytes 9 through 11 of the purge parameter list.) Note that some IOBs could be in a different protection key.

Figure 1. The IOB Chain

     Purge I/O Restore List
     ┌──────────────────────────────────────────────┐
     ³                                              ³
     ³     20(X'14')                                ³
     ³     ┌───────────────────────────────────┐    ³
┌────┼─────┤ Pointer to the first IOB. If 1s,  ³    ³
³    ³     ³ no I/O request was quiesced.      ³    ³
³    ³     └───────────────────────────────────┘    ³
³    ³                                              ³
³    └──────────────────────────────────────────────┘
³
└───→IOB(1) (where 1 is first IOB in chain)
     ┌──────────────────────────────────────────────┐
     ³                                              ³
     ³     IOBRESTR 25(19)                          ³
     ³     ┌───────────────────────────────────┐    ³
┌────┼─────┤ Pointer to the next IOB in the    ³    ³
³    ³     ³ chain.                            ³    ³
┴    ³     └───────────────────────────────────┘    ³
┬    ³                                              ³
³    └──────────────────────────────────────────────┘
³
└───→IOB(n) (where n is last IOB in chain)
     ┌──────────────────────────────────────────────┐
     ³                                              ³
     ³     IOBRESTR 25(19)                          ³
     ³     ┌───────────────────────────────────┐    ³
     ³     ³ Contains binary 1s.               ³    ³
     ³     ³                                   ³    ³
     ³     └───────────────────────────────────┘    ³
     ³                                              ³
     └──────────────────────────────────────────────┘