HP XP P9000 Continuous Access Synchronous for Mainframe Systems User Guide

Split and suspension 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 Cnt Ac-S or Cnt Ac-S Z 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 Cnt Ac-S 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 or suspend operation is in progress when I/O processing on Cnt Ac-S or Cnt Ac-S Z
pairs begins, the split operation on the pairs is given priority. After the pair is split, then the
I/O processing begins.
In a suspending operation, the IEA491E message displays on the mainframe host when pair
status changes to pair suspended-error.
In a suspending operation, the IEA491E message displays on the mainframe host when pair
status changes to pair suspended-error.
• Data consistency cannot be ensured when all of the following conditions exist:
- A port is blocked.
44 Planning for Continuous Access Synchronous Z