IBM DS8000 manual 1st

.

1st

	LSS11
Wait	This write operation is
	not completed because
	of extended long busy
	condition.

Servers

2nd

3rd

dependency for each write operation

LSS12

Wait

LSS13

Wait

These write operations are not completed because 1st write operation is not completed.

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.

134DS8000 Series: Concepts and Architecture