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Copy out-of-synchronous data

You can specify that only data updated on the source volume while the volume pair was

suspended is copied to its associated target volume.

Copy an entire volume or not copy the volume

You can copy an entire source volume to its associated target volume to guarantee that the source

and target volume contain the same data. When you establish volume pairs and choose not to

copy a volume, a relationship is established between the volumes but no data is sent from the

source volume to the target volume. In this case, it is assumed that the volumes contain the same

data and are consistent, so copying the entire volume is not necessary or required. Only new

updates are copied from the source to target volumes.

Global Mirror

Provides a long-distance remote copy across two sites by using asynchronous technology. Global

Mirror processing is most often associated with disaster recovery or disaster recovery testing.

However, it can also be used for everyday processing and data migration.
Global Mirror integrates both the Global Copy and FlashCopy functions.
The Global Mirror function mirrors data between volume pairs of two storage systems over greater

distances without affecting overall performance. It also provides application-consistent data at a

recovery (or remote) site in a disaster at the local site. By creating a set of remote volumes every few

seconds, the data at the remote site is maintained to be a point-in-time consistent copy of the data at

the local site.
Global Mirror operations periodically start point-in-time FlashCopy operations at the recovery site, at

regular intervals, without disrupting the I/O to the source volume, thus giving a continuous, near up-

to-date data backup. By grouping many volumes into a session that is managed by the master storage

system, you can copy multiple volumes to the recovery site simultaneously maintaining point-in-time

consistency across those volumes. (A session contains a group of source volumes that are mirrored

asynchronously to provide a consistent copy of data at the remote site. Sessions are associated with

Global Mirror relationships and are defined with an identifier [session ID] that is unique across the

enterprise. The ID identifies the group of volumes in a session that are related and that can participate

in the Global Mirror consistency group.)
Global Mirror supports up to 32 Global Mirror sessions per storage facility image. Previously, only one

session was supported per storage facility image.
You can use multiple Global Mirror sessions to fail over only data assigned to one host or application

instead of forcing you to fail over all data if one host or application fails. This process provides

increased flexibility to control the scope of a failover operation and to assign different options and

attributes to each session.
The DS CLI and DS Storage Manager display information about the sessions, including the copy state

of the sessions.

Practice copying and consistency groups

To get a consistent copy of your data, you can pause Global Mirror on a consistency group boundary.

Use the pause command with the secondary storage option. (For more information, see the DS CLI

Commands reference.) After verifying that Global Mirror is paused on a consistency boundary (state is

Paused with Consistency), the secondary storage system and the FlashCopy target storage system or

device are consistent. You can then issue either a FlashCopy or Global Copy command to make a

practice copy on another storage system or device. You can immediately resume Global Mirror,

without the need to wait for the practice copy operation to finish. Global Mirror then starts forming