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.

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.

Flashcopy consistency groups can be assigned to an ownership group. An ownership group defines a subset of users and objects within the system. You can create ownership groups to further restrict access to specific resources that are defined in the ownership group. Only users with Security Administrator roles can configure and manage ownership groups.

Ownership can be defined explicitly or it can be inherited from the user, user group, or from other parent resources, depending on the type of resource. Flashcopy consistency groups can be owned if they are assigned an ownership group explicitly or by inheritance from the user creating them. The following rules apply to FlashCopy consistency groups that are defined in ownership groups:

  • Users that are defined in ownership groups can add FlashCopy mappings to a consistency group if the volumes in the mapping and in the consistency group are within the same ownership group. For users that are not defined in an ownership group, no restriction for adding mappings to a FlashCopy consistency group. In this case, FlashCopy consistency groups are containers only and do not influence the ownership of the contents.
  • When you are migrating existing resources to ownership groups, a FlashCopy consistency group and its resources can belong to different ownership groups temporarily until the migration completes.
  • As with volume groups and volumes, the ownership of the consistency group has no impact in the ownership of the mappings it contains.

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.

Ownership groups are not supported for remote-copy consistency groups.