IBM DS8000 - Manual (Page 156)

134 DS8000 Series: Concepts and Architecture
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Figure 7-13 Consistency Group: Example1
Because of the time lag for Consistency Group operations, some volumes in some LSSs are
in an extended long busy state and other volumes in the other LSSs are not.
In Figure 7-13, the volumes in LSS11 are in an extended long busy state, and the volumes in
LSS12 and 13 are not. The 1st operation is not completed because of this extended long
busy state, and the 2nd and 3rd operations are not completed, because the 1st operation has
not been completed. In this case, 1st, 2nd, and 3rd updates are not included in the backup
copy. Therefore, this case is consistent.
See Figure 7-14 on page 135. In this case, the volumes in LSS12 are in an extended long
busy state and the other volumes in LSS11 and 13 are not. The 1st write operation is
completed because the volumes in LSS11 are not in an extended long busy state. The 2nd
write operation is not completed because of the extended long busy state. The 3rd write
operation is also not completed because the 2nd operation is not completed. In this case, the
1st update is included in the backup copy, and the 2nd and 3rd updates are not included.
Therefore, this case is consistent.
1st
2nd
3rd
dependency
for each write
operation
Servers
Wait
Wait
Wait
LSS11
LSS12
LSS13
These write operations
are not completed
because 1
st write
operation is not
completed.
This write operation is
not completed because
of extended long busy
condition.