HP StorageWorks XP Remote Web Console Software - Manual (Page 101)

Chapter 3 Preparing for Universal Replicator z/OS Operations 3-35
Hitachi Universal Replicator for IBM /OS User’s Guide
Figure 3-22 shows an example of a 3DC cascading configuration in which URz
and TCz Synchronous are combined. In this configuration, the volume in the
primary site is a TCz Synchronous main volume (M-VOL). The corresponding
TCz Synchronous remote volume (secondary data volume) is the volume in
the intermediate site, which is within a short distance from the primary site.
This TCz Synchronous remote volume is also used as a URz primary data
volume. The corresponding URz secondary data volume is the volume in the
secondary site, which is within a long distance from the intermediate site. If a
host issues an I/O to the TCz Synchronous main volume in the primary site,
data will be transferred via TCz Synchronous and URz to the secondary site
and will be restored to the secondary data volume.
R-VOL/Primary
data volume
Master
JNLVOL
Restore
JNLVOL
Primary
site Intermediate
site Secondary
site
TCz Synchronous (Short distance) URz (Remote distance)
M-VOL
Secondary
data VOL
Figure 3-22 3DC Cascading Configuration (Combining URz with TCz)
Data that is copied by TCz Synchronous is stored in the URz primary data
volume. If a failure occurs at the TCz Synchronous M-VOL, business tasks can
continue by using data in the URz secondary data volume containing data in
the TCz Synchronous M-VOL. Data in the TCz Synchronous M-VOL is restored
via URz to the secondary data volume in the secondary site, with update
sequence integrity ensured. If a failure occurs at both TCz Synchronous M-VOL
and secondary data volume due to a disaster or some other reason, disaster
recovery can be performed using the URz secondary data volume.
Note: A TCz Synchronous M-VOL must be created in a USP V storage system.
The fence level of the TCz Synchronous M-VOL must be Data (CRIT=Y
(ALL)).
Basic Behavior
This section explains the basic behavior of a 3DC cascading configuration
under the following conditions:
• The status of the TCz Synchronous pair is Duplex. The status of the URz
pair is also Duplex.
• A host in the primary site issues an I/O request to the TCz Synchronous M-
VOL