Complete this task to create a Metro Mirror consistency group.
In order to restart applications at a remote site successfully, data at the remote site must be consistent. The Metro Mirror consistency group function keeps data consistency at the remote site using consistency groups. A consistency group is a group of volumes that provides the ability to temporarily queue (at the host’s level) subsequent write operations to all consistency group volumes on a single LSS pairing when an error occurs to one of the volumes in the group (source or target), or when a total link failure is detected between the source and target LSS volume pair.
The consistency group function of Metro Mirror consists of two parts. One is the consistency group option and the other is the freeze and unfreeze operation. The freeze operation causes the storage unit to hold off I/O activity through the freezepprc command. The unfreeze operation allows I/O activities to resume when you issue the unfreezepprc command.
You can specify the consistency group option when you are defining Metro Mirror paths between pairs of LSSs or when you change the default consistency group setting on each LSS (the consistency group option is disabled by default) with the chlss command.
A group of volumes in a consistency group can consist of a combination of count-key-data volumes and fixed block volumes. In addition, the group of volumes in a consistency group can also consist of source volumes that are associated with a 1750 storage unit and target volumes that are associated with an ESS 2105 Model 800 or 750.
Perform the following step to define a path that has enabled the consistency group option for the volume pairs that are associated with the LSS volume pair. The example commands in this task are shown in two formats. The first format shows the type of information that the command requires. The second format provides the command with values declared for the variables.