Sessions

Copy sets

During data replication, data is copied from a source volume to one or more target volumes, depending on the session type. The source volume and target volumes that contain copies of the same data are collectively referred to as a copy set.

For more information about copy sets, see Copy sets.

Volume roles

A volume role is given to every volume in the copy set. The role defines how the volume is used in the copy set and, for multi-site sessions, the site location of the volume. For example, the H1 role is made up of host-attached volumes that are at site 1.

For more information about volume roles, see Volume roles.

Role pairs

A role pair is the association of two volume roles in a session that take part in a copy relationship. For example, in a Metro Mirror session, the role pair can be the association between host volumes at site 1 and host volumes at site 2 (H1-H2).

The flow of data in the role pair is indicated by an arrow. For example, H1>H2 denotes that H1 is the source and H2 is the target.

For more information about role pairs, see Role pairs.

Practice volumes

Practice volumes are volumes within a solution that can be used to practice disaster-recovery capability exactly as if there was a true disaster to recover to the remote site. You can use a practice volume to practice for disaster recovery without interrupting current data replication. Practice volumes are available in Metro Mirror, Global Mirror, Metro Global Mirror, and Metro Mirror - Global Mirror sessions.

You can practice disaster recovery actions without using practice volumes. However, without practice volumes, you cannot continue to copy data changes between volumes while you are practicing.

For more information about practice volumes, see Practice volumes.

Consistency groups

Copy Services Manager sessions are designed to maintain consistency across all the production volumes contained in a session. When Copy Services Manager refers to a consistency group, it is referring to the storage system container that the Copy Services Manager session is using to maintain consistency across all the volumes in the session. A storage system container, such as the DS8000® Global Mirror Master or the SAN Volume Controller Global Mirror consistency group, is created by Copy Services Manager so that the storage system knows which pairs to maintain consistency across.

Copy Services Manager automatically assigns an ID to each consistency group on the storage systems. However, you can choose to assign a custom name to a storage-system consistency group. A custom-defined name is used to associate multiple sessions with a specific storage-system consistency group.

For more information about consistency groups, see Working with user-defined consistency groups.

Data exposure

To manage data exposure, you can change the consistency-group interval time. The consistency-group time interval specifies how often a Global Mirror and Metro Global Mirror session attempts to form a consistency group. When you reduce this value, it might be possible to reduce the data exposure of the session. A smaller interval value causes the session to attempt to create consistency groups more frequently, which might also increase the processing load and message-traffic load on the storage systems.

Failover and failback operations

If a session has failover and failback capabilities, you can move the operation of Copy Services Manager from one site to another, and change the direction of the copy.

Failover is the process of temporarily switching production to a backup facility by following a scheduled maintenance period or a disaster at a production site. A failover operation can be followed by a failback operation, which is the process of returning production to its original location and resuming the copy between the two sites.

For more information about failover and failback operations, see Failover and failback operations.

Session commands

The commands that are available for a session depend on the session type.

For descriptions of the session commands for each session type, see Session commands.