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346 IBM System Storage DS6000 Series: Copy Services with IBM System z
4. Define the Global Mirror session and create a session ID between 1 and 255. You define
this session ID to the LSS that will become the Master, as well as to the LSSs in the
Subordinate storage disk subsystems that are going to participate in this session. Still the
Master LSS has not yet been appointed, which happens later when you start the session.
5. Populate the session with the Global Copy primary volumes (A). It is recommended that
the Global Copy primary volumes be added to the session once they have completed their
initial copy phase, also referred to as the “first pass.”
6. Start the session. This command actually defines the Master LSS. All further session
commands have to go through this LSS. You may also specify with the start command the
Global Mirror tuning parameters: maximum drain time, maximum coordination time, and
Consistency Group interval time.
Volumes can be added to the session at any time after the session number is defined to the
LSS where the volumes reside. Once the session is started, volumes can be added to the
session or can be removed from the session at any time.
Volumes may be added to a session in any state: simplex, pending, duplex, or suspended.
Volumes that have not completed their initial copy phase stay in a
join pending state until the
first pass is complete. If a newly added volume to a session is a primary suspended volume,
the first attempt to form a Consistency Group will fail. It is recommended to add only Global
Copy primary volumes that completed their initial copy phase.
When you plan to add a new Subordinate storage disk subsystem to an active session, you
have to stop the session first. Then add the new Subordinate storage disk subsystem and
start the session again with the updated RSESSION command, which then also contains the
new Subordinate storage disk subsystem.
When you add a new LSS to an active Global Mirror session, and this LSS belongs to a
storage disk subsystem that already has another LSS which belongs to the session, you may
just add the new LSS to the session without stop and start of the session. This is true for
either the Master storage disk subsystem or for a Subordinate disk subsystem.
26.3.1 Define paths
First you define paths from A to B; see Example 26-7 on page 347. These are the paths that
will be used for data transmission between the Global Copy pairs.
Note: If you still have not defined the paths between the Master LSS and the
Subordinate storage disk subsystem LSSs, then this is the time to do that before you
continue on.
Note: You only add Global Copy primary volumes to a Global Mirror session.