IBM DS6000 - Manual (Page 163)

Chapter 13. Metro Mirror options and configuration 139
Figure 13-3 Consistency Group: Example 2
In all cases, if each write operation is dependent, the Consistency Group option can keep the
data consistent in the Metro Mirror target volumes until the Consistency Group time-out
occurs. After the time-out value has been exceeded, all held I/O will be released. The
Consistency Group time-out value can be specified at the LSS level.
If each write operation is not dependent, the I/O sequence is not kept in the Metro Mirror
target volumes that are in LSSs with the Consistency Group option specified. In the example
illustrated in Figure 13-4 on page 140, the three write operations are independent. If the
volumes in LSS12 are in an
extended long busy
state and the other volumes in LSS11 and 13
are not, the first and third operations are completed and the second operation is not
completed.
1st
2nd
3rd
dependent write
operation
Application
on
Servers
Completed
Wait
Wait
LSS11
LSS12
LSS13
LSS21
LSS22
LSS23
Source DS6000 Target DS6000