IBM DS6000 - Manual (Page 316)

292 IBM System Storage DS6000 Series: Copy Services with IBM System z
23.7.7 Restart the application at the remote site
At this stage you may restart the application at the remote site and work with the consistent
set of B volumes; see Figure 23-15.
Figure 23-15 Restart applications at remote site
Note the primary suspended state of the B volumes, which implies change recording and
indicates the changed tracks on the B volumes.
When the local site is about to become ready to restart the applications again and resume the
operations, you prepare the remote site for the next step.
23.7.8 Prepare to switch back to the local site
Figure 23-16 Failback operation from B to A in preparation for returning to local site
The local site is back and operative again. We assume that the local site did not lose the data
at the time when the swap to the remote site was done. It is then possible to resynchronize
the changed data from B to A before restarting the application at the local site. This is
accomplished doing a Failback operation (Copy Services Failback function) from B to A; see
Figure 23-16.
Global Copy
Primary
Primary
A
Primary
Primary
A
Tertiary
C
Primary
Primary
A
Primary
Primary
A
B
Remote site
Primary
Primary
A
Primary
Primary
A
Primary
A
PENDING
Host
Primary
SUSPENDED
Restart applications
Local site
Global Copy Primary
Primary
A
Primary
Primary
A
Tertiary
C
Primary
Primary
A
Primary
Primary
A
B
Remote site
Host
Primary
Failback B to A
Primary
Primary
A
Primary
Primary
A
A
PENDING
Secondary
PENDING
Resync from B to A
Local site