An active-active relationship is used
to manage the synchronous replication of volume data between two sites.
You must make the master volume accessible through either I/O group.
The synchronizing process starts after change volumes are added to
the active-active relationship.
When you work with active-active relationships, follow these guidelines and requirements:
- An active-active volume is made by making an active-active relationship between the master and
auxiliary volume copy.
- Active-active volumes can also use change volumes, which hold earlier consistent revisions of
data when changes are made. A change volume must be created for both the master volume and the
auxiliary volume of the relationship.
- An existing single copy volume can be converted to an active-active volume. An auxiliary volume
is created at the other site and an active-active relationship between the master and auxiliary
volume is made. Master and auxiliary change volumes must be added to the relationship so that the
master and auxiliary copies can be synchronized. For high availability, a host access I/O group that
is local to the auxiliary copy must be added.
- A new active-active volume can be created by first making a master volume and an auxiliary
volume and then making the active-active relationship between them.
- The two volumes in an active relationship must be the same size. The change volumes must be the
same size and in the same site as the associated master volume or auxiliary volume.
- For ease of application management, an active-active relationship can be added to a consistency
group.
Note: Membership of a consistency group is an attribute of the relationship, not the
consistency group. Therefore, issue the chrcrelationship command to add or remove
a relationship to or from a consistency group.
States
Active-active relationships can be in one of the following states:
- InconsistentStopped
- The relationship does not have both change volumes defined.
- InconsistentCopying
- The relationship is performing initial synchronization of data to the second copy.
- ConsistentStopped
- Either the relationship was created with -sync and does not have both change volumes defined or
a change volume was force-deleted after the relationship synchronized.
- ConsistentSynchronized
- The two copies both contain all completed host-write operations. The high availability failover
and read pass-through options are both available.
- ConsistentCopying
- The two copies are different, but resynchronization occurs when it can. During the copy, the
status field is online. When the system is unable to copy, the status field shows what is preventing
the copy.
- Idling
- Manual intervention was used to restore access to a historical copy of the relationship.