HP 9000 rp5405 Servers - Manual (Page 166)

N: This type of pair group cannot be connected.
Requirements for the copy type when creating a cascade configuration (mainframe systems)
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 Access
Synchronous
Business Copy
Y Y Y N Business Copy
Y N N Y
Continuous Access
Synchronous
N N N Y
Continuous Access
Asynchronous
N N Y Y
Continuous Access
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
Managing pair life cycle 166