The host issues an update to the Continuous Access Synchronous Z primary volume (M-VOL), which
is copied synchronously to the R-VOL. The Continuous Access Journal Z system copies the
synchronous S-VOL data to the Continuous Access Journal Z remote site.
Data in the Continuous Access Journal Z S-VOL is an asynchronous copy of the Continuous Access
Synchronous Z M-VOL. Depending on RPO and bandwidth, Continuous Access Journal Z S-VOL
data can be very close to P-VOL data. As always with Continuous Access Journal Z, data consistency
is insured.
Figure 20 3 data center cascade (3DC cascade)
Failure recovery occurs as follows:
• If a failure occurs at the Continuous Access Synchronous Z M-VOL, business continues because
data in the Continuous Access Journal Z S-VOL is restored to the production system via the
intermediate volume, if needed. Update sequence integrity is insured.
• If a failure occurs at both Continuous Access Synchronous Z M-VOL and R-VOL, an implemented
disaster recovery plan would re-direct host activities to the Continuous Access Journal Z S-VOL.
See “Recovery in a 3DC cascade configuration ” (page 106) for recovery information and
procedures.
Prerequisite information for 3DC cascade
• P9500 must be installed at the local, Continuous Access Synchronous Z intermediate, and
Continuous Access Journal Z remote sites.
• Business Continuity Manager is recommended at all sites.
• Remote Web Console is required at all sites.
Host application◦
◦ Continuous Access Synchronous Z
◦ Continuous Access Synchronous Z primary volume (M-VOL), the primary production
volume
◦ Continuous Access Synchronous Z fence level must be Data (CRIT=Y (ALL)).
• The intermediate site requires the following:
Continuous Access Synchronous Z◦
◦ Continuous Access Journal Z
◦ Continuous Access Synchronous Z R-VOL = Continuous Access Journal Z P-VOL
◦ Continuous Access Journal Z master journal volume
• The remote site requires the following:
Continuous Access Journal Z◦
◦ Continuous Access Journal Z S-VOL
◦ Continuous Access Journal Z remote journal volume
• Differential data is used to resynchronize a suspended Continuous Access Synchronous Z or
Continuous Access Journal Z pair.
3 data center cascade configuration 131
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