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About delta resync – HP XP P9000 Command View Advanced Edition Software User Manual

Page 161

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Copy type of the pair group to be connected by group addition

Copy type of
the original pair
group

Continuous Ac-
cess Journal

Continuous Access
Asynchronous

Continuous Ac-
cess Synchron-
ous

Snapshot

Business
Copy

Y

N

N

Y

Y

Continuous Ac-
cess Synchronous

N

N

N

Y

Y

Continuous Ac-
cess Asynchron-
ous

N

N

N

Y

Y

Continuous Ac-
cess Journal

Legend:

Y: This type of pair group can be connected.

N: This type of pair group cannot be connected.

Permitted topologies for cascade and multi-target configurations

The following restrictions apply when creating cascade or multi-target configurations or deleting copy
groups in cascade or multi-target configurations:

When creating a cascade configuration, it is necessary to first create a higher-level copy group.
Higher-level copy groups cannot be added to lower-level copy groups

When creating a cascade configuration, copy types and pair statuses of related copy groups must
be compatible

When deleting copy groups from a cascade configuration, you must first delete all lower-level
copy groups before deleting a higher-level copy group

The number of pairs that can be created varies depending on the storage system and copy type

About delta resync

In a 3DC multi-target configuration, there is one primary site and two secondary sites. Continuous
Access Synchronous and Continuous Access Journal are used to copy storage system volumes among
the three sites (called a data center). Continuous Access Journal provides the primary site and
Continuous Access Synchronous and Continuous Access Journal provide the secondary sites. Replication
Manager can be used to configure a Delta Resync pair using the two secondary sites. Delta Resync
pairs are stand-by pairs for providing additional redundancy in 3DC multi-target configurations.

Continuous Access Journal provides the delta resync operation as a way to recover from failures in
the primary site. If a failure occurs at the primary site in a 3DC multi-target configuration, the P9000
RAID Manager

horctakeover

command is used to reconfigure the Continuous Access Synchronous

secondary site as the primary site. If the delta re-synchronization function is used between the primary
and secondary sites, journal-copying of only the minimum data required is performed following a
failure, minimizing the recovery time.

Related topics

Creating a 3DC multi-target configuration

, page 162

Limitations when performing 3DC configuration pair operations (mainframe systems)

, page 162

User Guide

161

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