HP XP7 Storage - Manual (Page 143)

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The response time for host I/Os will be the response time for Cnt Ac-S Z operation plus the
creation time of journal data in the intermediate site.
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The utilization rate on the local site with a 3DC cascade configuration is higher than if Cnt
Ac-J Z and a Cnt Ac-S Z systems are used independently.
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If you perform a Compatible FlashCopy copy operation on the Cnt Ac-S Z pair, the Cnt Ac-S
Z pair status becomes Pending Duplex, and the Cnt Ac-J Z pair is suspended.
Procedure for setting up 3DC cascade
Procedure 44 To set up a 3DC cascade configuration
1. Install and set up Cnt Ac-S Z and Cnt Ac-J Z on the required systems.
2. Create the Cnt Ac-S Z pair on the primary system. See HP XP7 Continuous Access Synchronous
for Mainframe Systems User Guide for instructions.
3. When Cnt Ac-S Z pair status is Duplex, create the Cnt Ac-J Z pair on the secondary system
using the Cnt Ac-S Z S-VOL as the Cnt Ac-J Z P-VOL. The Cnt Ac-J Z operation is rejected by
the system if Cnt Ac-S Z pair status is not already Duplex.
Mirror ID must be set between 1 and 3.
3DC multi-target configuration
In a multi-target configuration, data is copied from the local site to two remote sites.As illustrated
below, the P-VOL is paired with the Cnt Ac-S Z secondary volume and the Cnt Ac-J Z S-VOL at
separate remote sites in a 3DC multi-target configuration. The Cnt Ac-S Z site is at an intermediate
distance; the Cnt Ac-J Z site is located at a greater distance.
Figure 19 3-data-center multi-target configuration
The host issues an update to the production volume and, synchronously, to the Cnt Ac-S Z S-VOL.
As with a standalone Cnt Ac-J Z system, the update data is asynchronously written from the primary
volume (P-VOL) to the Cnt Ac-J Z S-VOL.
The benefit of this configuration is that it provides a third copy of the data, helping to ensure that
business can continue in the event of a failure at the other two sites.
Failure recovery occurs as follows:
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If a failure occurs in the P-VOL, business is resumed using the Cnt Ac-S Z S-VOL. When the
failure is corrected at the local site, business tasks are transferred back to the local site.
In addition, a quick disaster recovery solution can be put in place while the local site is being
restored, using a Cnt Ac-J Z pair for delta resync. In this configuration, the Cnt Ac-S Z S-VOL
3DC multi-target configuration 143