HP XP7 Continuous Access Synchronous for Mainframe Systems User Guide (TK911-96003)

Split behaviors for pairs in a CG
When the pairs in a consistency group receive updates while in the process of being split or
suspended, or when they are about to be split or suspended, S-VOL data consistency is managed
as follows:
• If I/O processing is in progress on pairs in the same consistency group, and the split or suspend
operation begins, the I/O processing completes first, then the split/suspend operation is run.
The following figure shows that I/O processing completes first; then the pair split operation
for the pair on Volume B completes.
The following figure shows data in track 2 being copied to the S-VOL, and the data in track 3
becomes differential data. In this case, track 2 is used for I/O processing to the volume in the
consistency group when the split command is issued to the pair.
• If a split operation is in progress when I/O processing on the pairs begins, the split operation
on the pairs is given priority. After the pair is split, then the I/O processing begins.
In a split operation, the IEA491E message displays on the mainframe host when pair status
changes to pair split-error.
In a split operation, the IEA491E message displays on the mainframe host when pair status
changes to pair split-error.
• Data consistency cannot be ensured when all of the following conditions exist:
- A port is blocked.
- A split command is in progress.
- I/O processing begins.
44 Planning for Continuous Access Synchronous Z