HP StorageWorks XP Remote Web Console Software - Manual (Page 50)

2-28 Chapter 3 Preparing for Universal Replicator z/OS Operations
Hitachi Universal Replicator for IBM /OS User’s Guide
• Journal data stored in the restore journal volume
The journal data is read from the restore journal volume to cache. The
journal data that is read to cache is copied to the existing cache track and
promoted to formal data. After that, the space for the restore journal
volume is released.
URz Delta Resync Operation
When you are using URz and TCz Synchronous in a 3DC multi-target
configuration, URz provides delta resync operation as one of the solutions for
failures in primary site. In a 3DC multi-target configuration, there are one
primary site and two secondary sites; TCz Synchronous and URz secondary
sites. For detailed information about 3DC multi-target configuration, see
section TCz Synchronous (3DC Multi-target Configuration).
If a failure occurs on the primary site in 3DC multi-target configuration, you
need to use Business Continuity Manager to use the TCz Synchronous
secondary site as the primary site. If you perform a delta resync operation
after the TCz Synchronous secondary site becomes a primary site. The URz
pair will be restored quickly by the delta resync operation, you will not need to
wait for a long time before you can use the URz data volumes again.
Delta resync operation consists of the two processes; one is the process for
the preparation before the failure occurs, the other is the process for the
recovery after the failure occurs.
• Processing for the preparation before the failure occurs (see the next
section)
• Processing for the recovery after the failure occurs (see section Switching
the Master Journal Group of URz)
Journal Obtain in TCz Synchronous Secondary Site
To perform delta resync operation when a failure occurs, you also need to
obtain the journal data in the TCz Synchronous secondary site of 3DC multi-
target configuration. Specify the TCz Synchronous R-VOL in TCz Synchronous
secondary site as the primary data volume, and specify the data volume in
URz secondary site as the secondary data volume, in order to create a URz
pair for the delta resync operation.
When you create a URz pair for delta resync operation, the differential data of
data volumes in TCz Synchronous primary site and secondary site will be
stored in the journal volumes in TCz Synchronous secondary site as journal
data. The following figure shows an example.