VSO options with XRF

During the tracking and takeover phases on the alternate IMS, log records are processed in the same manner as during active IMS emergency restart (from a previous active system checkpoint to the end of the log).

The alternate IMS uses the log records to determine which areas have committed updates that were not written to DASD before the failure of the active IMS. If any such committed updates are found, the alternate will REDO them, following the same process as for active IMS emergency restart.

During tracking, the alternate uses data spaces to track VSO area updates: in addition to the data space resources used for VSO areas, the alternate obtains a single non-DREF data space which it releases at the end of takeover. If XRF tracking or takeover is unable to get the data space or main storage resources it needs to perform VSO REDO processing, the area is stopped and marked recovery needed.

Following an XRF takeover, areas that were open or in the data space remain open or in the data space. The VSO options and PREOPEN|NOPREO options that were in effect for the active IMS before the takeover remain in effect on the alternate (the new active) after the takeover. Note that these options may not match those defined to DBRC. For example, a VSO area removed from virtual storage by the /VUNLOAD command before the takeover is not restored to the data space after the takeover.

VSO areas defined with the preload option are preloaded at the end of the XRF takeover. In most cases, dependent regions can access the area before preloading begins, but until preloading completes, some area read requests may have to be retrieved from DASD.