Volume groups

A volume group is a container for managing a set of related volumes as a single object. The volume group provides consistency across all volumes in the group.
Volume groups can be used with the following functions:
Safeguarded Copy function
One implementation of volume groups is to group volumes to be configured as Safeguarded. Safeguarded copy function is a cyber-resiliency feature that creates immutable copies of data that cannot be changed or manipulated.

A Safeguarded volume group describes a set of source volumes that can span different pools and are backed up collectively with the Safeguarded Copy function. Safeguarded snapshots are supported on the system through an internal scheduler that is defined in the snapshot policy or can be configured with an external snapshot scheduling application such as IBM Copy Services Manager. For more information, see Safeguarded snapshot.

Policy-based replication

You can use volume groups for policy-based replication. Policy-based replication is configured on all volumes in a volume group by assigning a replication policy to that volume group. The system automatically replicates the data and configuration for volumes in the group based on the values and settings in the replication policy. As part of policy-based replication, a recovery volume group is created automatically on the recovery system. Recovery volume groups cannot be created, changed, or deleted. A single replication policy can be assigned to multiple volume groups to simplify replication management. When additional volumes are added to the group, replication is automatically configured for these new volumes. Policy-based replication supports configuration changes while the partnership is disconnected. After the partnership is reconnected, the system automatically reconfigures the recovery system.

Note: If you assign a replication policy before you create new volumes, the initial synchronization of volumes is skipped. In this case, the recovery copy of the volumes can be used immediately.
Snapshot function
Snapshots are the read only point-in-time copies of a volume group that cannot be directly accessible from the hosts. To access the snapshot contents, you can create a clone or thin clone of a volume group snapshot. You can use the command-line interface or management GUI to configure volume groups to use snapshot policies for multiple volumes for consistent management. Snapshots will always be in the same pool as the parent volume, and the I/O group of the snapshot will be same as the parent volume. Safeguarded snapshot with internal scheduler can be created by using snapshot function.

The volumes in a volume group are supposed to be mutually consistent. This means that volume group only make sense as a group. When a group of thin-clone or clone is populated, it is snapshot function's responsibility to ensure that the images are mutually consistent. When volumes are added or removed from a group, the host applications ensures the volume groups are mutually consistent.