The host issues an update to the production volume and, synchronously, to the Continuous Access
Synchronous S-VOL. As with a standalone Continuous Access Journal system, the update data is
asynchronously written from the primary volume (P-VOL) to the Continuous Access Journal S-VOL.
The benefit of this configuration is that it provides a third copy of the data, helping to insure 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 Continuous Access Synchronous
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 Continuous Access Journal pair for delta resync. In this configuration,
the Continuous Access Synchronous S-VOL is paired with the Continuous Access Journal S-VOL.
See “Delta resync configuration ” (page 138) for more information.
• If a failure occurs in the Continuous Access Synchronous system ( P-VOL and S-VOL), business
is resumed using the Continuous Access Journal S-VOL. When the failure is corrected, business
tasks are transferred back to the primary site.
• If a failure occurs in the Continuous Access Journal system (P-VOL and S-VOL), business is
resumed using the Continuous Access Synchronous S-VOL.
See “Recovering from primary site disaster in 3DC multitarget configuration” (page 97) for recovery
information and procedures.
Prerequisite information for 3DC multitarget
• P9500 must be installed at the local, Continuous Access Synchronous intermediate, and
Continuous Access Journal remote sites.
• RAID Manager is recommended at all sites.
• Remote Web Console is required at all sites.
• The primary site requires the following:
Continuous Access Synchronous◦
◦ Continuous Access Journal
◦ Continuous Access Synchronous P-VOL = Continuous Access Journal P-VOL. This is the
primary production volume.
◦ Continuous Access Journal master journal volume
• The intermediate site requires the following:
Continuous Access Synchronous◦
◦ Continuous Access Journal
◦ Continuous Access Synchronous S-VOL
• The remote site requires the following:
Continuous Access Journal◦
◦ Continuous Access Journal S-VOL
◦ Continuous Access Journal remote journal volume
• 3DC multitarget is not supported for multiple primary and secondary systems.
Procedure for setting up 3DC multitarget
To set up a 3DC cascading configuration
1. Install and setup Continuous Access Synchronous and Continuous Access Journal on the
required systems.
3DC multitarget configuration 137
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