Splitting a UR pair

When you split a pair, write-data is no longer sent to the S-VOL and the pair is no longer synchronized. Splitting a pair or mirror gives you a point-in-time copy of the P-VOL.

Before you begin

• This operation can be performed from the primary or secondary storage system.

• Pair status must be COPY or PAIR.

• To split multiple pairs at the same time, the pairs must belong to the same mirror. This ensures sequence consistency among S-VOLs in the mirror.

• Pairs in a CCI consistency group consisting of multiple primary and secondary storage systems can only be split in the mirror.

The following additional information may be useful before beginning the procedure:

• Performing the pair split when I/O load is low reduces impact on performance. Operations on multiple pairs in the same consistency group with different statuses may result in suspension during periods of heavy write I/O.

• If you split pairs in PAIR status and other than PAIR status in the same mirror, an unexpected suspension could occur during the operation under heavy I/O load conditions. You can estimate whether the I/O load is heavy or not from frequency of host I/Os. This operation should be performed under light I/O load conditions.

• During normal operations, the secondary storage system rejects write operations to an S-VOL. If desired, you can enable write operations to the S-VOL while the pair is split by enabling the S-VOL write option. When this option is enabled, the secondary storage system sends the S-VOL track bitmap to the primary storage system during pair resync to ensure proper resynchronization of the pair. The S-VOL write option (Secondary Volume Write) is described in the pair-split procedure.

Procedure

1. Open the Remote Replication window:

In Command Suite:

1. On the Resources tab, expand the Storage Systems tree.

2. Right-click the target storage system, and click Remote Replication.

In Device Manager - Storage Navigator:

1. In the Explorer pane, expand the Storage Systems tree.

2. Expand the target storage system tree, expand Replication, and click Remote Replication.

2. In the UR Pairs tab, select the pairs to be split and click Split Pairs.

3. In the Split Pairs window, review the pairs to be split in the Selected Pairs table. To remove a pair from the table, select the pair and click Cancel.

4. For Secondary Volume Write, specify whether data can be written to the S-VOL while it is split. Available only when performing the split operation from the pair’s primary storage system.

• Enable: The host can write data to the S-VOL.

• Disable: The host cannot write data to the S-VOL.

 In a 3DC configuration in which three UR sites are combined, host I/O write requests to the split pair's S-VOL might be rejected when the delta resync pair shares the split S-VOL, even if you split a pair with the Secondary Volume Write option enabled.

5. Click Finish.

6. In the Confirm window, review the settings, enter a task name, and then click Apply.