3DC multi-target configuration

In a multi-target configuration, data is copied from the primary site to two secondary sites. As shown in the following illustration, the P-VOL is paired with the TC secondary volume and the UR S-VOL at separate secondary sites in a 3DC multi-target configuration. The TC site is at an intermediate distance; the UR site is located at a greater distance.

The host issues an update to the production volume and, synchronously, to the TC S-VOL. As with a standalone UR system, the update data is asynchronously written from the primary volume (P-VOL) to the UR S-VOL.

The benefit of this configuration is that it provides a third copy of the data, helping to ensure that business can continue in the event of a failure at the other two sites.

Failure recovery occurs as follows:

• If a failure occurs in the P-VOL, business is resumed using the TC S-VOL. When the failure is corrected at the primary site, business tasks are transferred back to the primary site.

In addition, a quick disaster recovery solution can be put in place while the primary site is being restored, using a UR delta resync pair. In this configuration, the TC S-VOL is paired with the UR S-VOL. See Delta resync configuration for more information.

• If a failure occurs in the TC system (P-VOL and S-VOL), business is resumed using the UR S-VOL. When the failure is corrected, business tasks are transferred back to the primary site.

• If a failure occurs in the UR system (P-VOL and S-VOL), business is resumed using the TC S-VOL.

For recovery information and procedures, see the section "Recovery for 3DC UR/TC multi-target configuration" in the Universal Replicator User Guide.