If you share SIz P-VOLs in a storage system with TCz or URz S-VOLs, you can use consistency group (CTG) pair-split to keep SIz S-VOLs consistent.
When an SIz P-VOL shares a URz or TCz S-VOL to create pairs, you can assign the same CTG ID to the SIz pairs in order to use the CTG pair-split function to maintain consistency among the SIz S-VOLs.
Note: Consistency among the SIz P-VOL, URz S-VOLs, and TCz S-VOLs can be maintained only if the volumes have the same status, and consistency with URz S-VOLs can be maintained only if the volumes are registered in the same journal.
The following image illustrates CTG pair-split with TCz.
The following image illustrates CTG pair-split with URz.
When you perform a CTG pair-split on shared URz P-VOLs, the following operations occur:
- URz restores the journal data that was created before you restored the split time to URz S-VOLs (SIz P-VOLs). Note: If an SIz pair is suspended due to a failure, the split time and the actual task start time must be the same in order to restore URz journal data that you created before the split time to the URz/SIz 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.
- URz detects restore journal (R-JNL) data with a time stamp later than the registered split time and suspends R-JNL operations.
- The SIz pair is split.
- URz resumes the suspended R-JNL operations.