Splitting pairs

You split TrueCopy pairs when you migrate data, when you recover data, or when you perform tasks on TrueCopy pairs like assigning pairs to consistency groups.

Splitting pairs suspends data copying to the S-VOL.

When you split a pair, the following occurs:

• I/O writes from the host continue to the P-VOL but stop to the S-VOL.
• Any current update copy operation completes to the S-VOL, ensuring data consistency to the point of the split operation.
• The pair status changes to PSUS.
• The primary storage system records the updated tracks to the P-VOL that occur after the split as differential data. This data is copied to the S-VOL when the pair is resynchronized.
• To access an S-VOL of which write option is enabled, the pair must be split.
• When a pair is split, the secondary storage system completes pending copy operation before changing the pair status to ensure pair synchronization.
• You can set an option to block updates to the P-VOL while the pair is split. This results in the P-VOL and S-VOL staying synchronized.
• Another option is to enable system write to the S-VOL from a host. The secondary storage system records the updated tracks as differential bitmaps. When the pair is resynchronized, the secondary storage system sends the differential bitmaps to the primary system, which merges all differential bitmaps to determine which tracks are out-of-sync.