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.

TCz Synchronous (Short distance)

 

URz (Remote distance)

M-VOL

R-VOL/Primary

Secondary

data volume

 

data VOL

 

 

Primary

Intermediate

Master

Restore Secondary

site

JNLVOL

JNLVOL site

site

 

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

Chapter 3 Preparing for Universal Replicator z/OS Operations

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Hitachi Universal Replicator for IBM /OS User’s Guide

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Hitachi MP-96RD625-01 manual Basic Behavior, 22 3DC Cascading Configuration Combining URz with TCz