There are PPRC paths in place from the primary volume to the secondary
and also from the secondary to the primary. The source and target
volumes have equivalent device geometry. In this situation, selecting "switch
pair, and swap" directs P/DAS to perform the following actions:
- End the current PPRC pair.
- Establish a new PPRC pair (with NOCOPY) to activate copying in
the reverse direction (from the target device tttt to the
source device ssss).
- Immediately suspend the PPRC operation. All changes made to target
device tttt are recorded in the bit maps for the operation,
but are not to be copied to the original source device ssss.
- Redirect all application I/O to target device number tttt.
The change is transparent to the application programs. P/DAS only
sends I/Os to the secondary volume from this point on, and the primary
and secondary volumes will no longer contain the same information.
The changes that occur between the swap operation and the subsequent
resynchronization of the volume pairs are maintained on the old secondary
volume. P/DAS will copy the changed updated tracks back to the original
primary volume, and will make the volumes duplexed PPRC pairs again.