Using consistency group pair-split with shared volumes

If you share SI P-VOLs in a storage system with TC or UR S-VOLs, you can use consistency group (CTG) pair-split to keep SI S-VOLs consistent.

When an SI P-VOL shares a UR or TC S-VOL to create pairs, you can assign the same CTG ID to the SI pairs in order to use the CTG pair-split function to maintain consistency among the SI S-VOLs.

The following image illustrates CTG pair-split with TC.

The following image illustrates CTG pair-split with UR.

When you perform a CTG pair-split on shared UR P-VOLs, the following operations occur:

1. UR restores the journal data that was created before you restored the split time to UR S-VOLs (SI P-VOLs).
   Note: If an SI pair is suspended due to a failure, the split time and the actual task start time must be the same in order to restore UR journal data that you created before the split time to the UR/SI volume after the split. The task start time is determined by the amount of journal data in the journal volume at the time of the split.

   For example, if the journal volume contains data that needs one hour to be restored, the starting time of the split operation delays for an hour.

2. The SI pair is split.
3. UR resumes the suspended R-JNL operations.