Consistency groups

A consistency group is an optional container for FlashCopy® mappings or remote-copy relationships. When you use a consistency group, you can complete copy operations on the entire group instead of the individual mappings.

You can add many mappings or relationships to a consistency group. Review and consider the following guidelines:

FlashCopy mappings and remote-copy relationships cannot exist in the same consistency group.
Relationships can be added to consistency groups if the state of the relationship matches the state of the consistency group.
To enable consistency protection for a consistency group, consistency protection must be enabled on each relationship within that consistency group.
For example, if a consistency group consists of four Metro Mirror relationships that are configured with secondary change volumes, the data of the entire consistency group can be protected during resynchronization. However, if a secondary change volume is not configured on one of the Metro Mirror relationships, consistency protection is lost for all of the relationships within the consistency group.

The system supports the following types of consistency groups:

FlashCopy consistency groups: A FlashCopy consistency group is a container for FlashCopy mappings to help manage related copies and ensure consistency. You can add many mappings to a consistency group.
The consistency group is specified when the FlashCopy mapping is created. You can also add existing FlashCopy mappings to a new consistency group or change the consistency group later. When you use a consistency group, you prepare and start that group instead of the individual FlashCopy mappings. This process ensures that a consistent copy is made of all the source volumes. FlashCopy mappings to control at an individual level are known as stand-alone mappings. Do not place stand-alone mappings into a consistency group because they become controlled as part of that consistency group.

Remote Copy Consistency Groups: You can group remote-copy relationships into a consistency group so that they can be updated at the same time. A command that is issued to the consistency group is simultaneously applied to all of the relationships in the group.