Chapter 11. Advanced Copy Services 533
The relationship status changes to consistent synchronized when the resynchronization 
process completes. The relationship automatically resumes replication after the temporary 
loss of connectivity.
Change Volumes used for Consistency Protection are not visible and manageable from the 
GUI because they are used for Consistency Protection internal behavior only.
It is not required to configure a secondary change volume on a MM/GM (without cycling) 
relationship. However, if the link goes down or the secondary volume is offline, the 
relationship goes in to the Consistent stopped status. If write operations take place on either 
the primary or secondary volume, the data is no longer synchronized (Out of sync).
Consistency protection must be enabled on all relationships in a Consistency Group. Every 
relationship in a Consistency Group must be configured with a secondary change volume. If a 
secondary change volume is not configured on one relationship, the entire Consistency 
Group stops with a 1720 error if host I/O is processed when the link is down or any secondary 
volume in the Consistency Group is offline. All relationships in the Consistency Group are 
unable to retain a consistent copy during resynchronization.
The option to add consistency protection is selected by default when MM/GM relationships 
are created. The option must be cleared to create MM/GM relationships without consistency 
protection. 
11.6.21  Valid combinations of FlashCopy, Metro Mirror, and Global Mirror 
Table 11-10 lists the combinations of FlashCopy and MM/GM functions that are valid for a 
single volume.
Table 11-10   Valid combination for a single volume
11.6.22  Remote Copy configuration limits
Table 11-11 lists the MM/GM configuration limits.
Table 11-11   Metro Mirror configuration limits
FlashCopy Metro Mirror or Global Mirror 
source
Metro Mirror or Global Mirror 
target
FlashCopy Source Supported Supported
FlashCopy Target Supported Not supported
Parameter Value
Number of Metro Mirror or Global Mirror 
Consistency Groups per system
256 
Number of Metro Mirror or Global Mirror 
relationships per system
8192
Number of Metro Mirror or Global Mirror 
relationships per Consistency Group
8192