IBM System storage DS6000 Series, Redbook

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IBM System Storage DS6000 Series: Copy Services with IBM System z
FCQUERY Formatted -2
DEVN SSID LSS CCA CU SERIAL ACT MAX XC PC CC RV SEQNUM
6403 0002 00 03 1750 0000000AAVCA 1 50099 N S N N 42B03957
FCQUERY COMMAND COMPLETED FOR DEVICE 6403. COMPLETION CODE: 00
Example 23-5 shows, for each single FlashCopy relationship, a column titled RV , which stands
for
revertible
. An N indicates that this FlashCopy relationship is not revertible and all changes
are committed. All volumes show the same information for RV . The other column that you have
to check is the SEQNUM or FlashCopy sequence number. This number is also identical for all
four volumes in Example 23-5, which is good information. This leads you to conclude that:
򐂰 All FlashCopy pairs are non-revertible.
򐂰 All FlashCopy sequence numbers are equal.
No further action is necessary and the set of C volumes is consistent and a good copy.
Figure 23-13 shows the consistency group creation process. The action required depends on
the state of the consistency group creation process when the failure occurred.
Figure 23-13 FlashCopy consistency group creation process
Depending on when the failure occurs, there are some combinations of revertible states and
FlashCopy sequence numbers that need different corrective actions. Use Table 23-1 as a
guide. This is a decision table that is read in the following way: When column 2
and
column 3
are true, then take the action in column 4. Column 5 contains additional comments. Do this
for each of the four cases. The cases are described in chronological order, starting from the
left.
Table 23-1 Consistency Group and FlashCopy validation decision table
Create consistency group by holding
application writes while creating
bitmap containing updates for this
consistency group on all volumes -
design point is 2-3ms
Maximum coordination time (eg. 10ms)
Drain consistency group and send
to remote DS using Global Copy.
Application writes for next
consistency group are recorded in
change recording bitmap
Maximum drain time – eg.1 min
Transmit updates in Global Copy mode
while between consistency groups
Consistency group interval – 0s to 18hrs
Start next consistency group
FlashCopy issued
with revertible option
FlashCopy committed
once all revertible
Flashcopies have
successfully completed
Action required
All FlashCopies
revertible
Are all FC
relationships
revertible? Are all FC sequence
numbers equal? Action to take Comments
Case 1 NO. YES. No action needed. All
C volumes are
consistent. CG formation ended.