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, and then the split/suspend operation is performed.
The following figure shows that I/O processing is completed first, and then the pair split operation for the pair on Volume B is completed.
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, the I/O processing begins.
- 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.
In such a case, resynchronize the consistency group, and then issue the split command again.