IBM System storage DS6000 Series, Redbook

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Chapter 26. Global Mirror examples
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26.2.5 Timing information
Creating consistency groups relies also on internal timing information. It is important to
understand that the internal timer in the DS6000 is not synchronized with an external clock.
Example 26-6 shows an RQUERY command example with a TIME command just before the
RQUERY command. The TSO TIME command displays the CPU based timer, which displays
10:09:32 . Consistency Group drain time limit is 60 seconds or one minute. RQUERY displays
the internal disk subsystem clock time with 14:37:59 as the time of the last good Consistency
Group. Both timers are about 4 1/2 hours apart from each other. Even with a few failed
attempts to form Consistency Groups, the disk subsystem clock time would be just a few
minutes behind the CPU-based clock.
Example 26-6 Internal timer is not synchronized with external timer
TIME-10:09:32 AM. CPU-00:00:00 SERVICE-255 SESSION-00:00:00 JUNE 17,2005
READY
RQUERY VOLSER(AA601F) ACTION(GMLSTAT)
RQUERY Output Volser(AA601F) Action(GMLSTAT) Version(001)
SNbr GMLStat GoodCg Pct CrnBadCG TotBadCG LastGoodCGSCntlClock
-- ---------- -------- --- -------- -------- --------------------
01 Running 00000125 98 00000003 00000005 17 Jun 2005 14:37:59
. .
Master: Serial SSID LSS CGInt CGDrn CrdInt
------------ ---- -- ----- ----- -----
0002013AAGXA 2060 00 15 60 5
. .
BadCGrpFormation: When Serial SSID LSS Reason Activity
----- ------------ ---- --- ---------- ----------
Last 0002013AAGXA ???? FF DrTimeExcd DrnInPrg
Prev 0002013AAGXA ???? FF DrTimeExcd DrnInPrg
First 0002013AAGXA 2060 00 CmdRej FC4 RunInPrg
READY
Note that you cannot rely on the internal disk subsystem clock time information as an
absolute wall clock timing type. You may set the internal disk subsystem clock time with the
help of an IBM customer engineer as close to the actual wall clock as possible.
26.3 Set up the Global Mirror environment using TSO
The following sequence of examples shows how to set up a Global Mirror environment using
TSO commands. Most steps to create a Global Mirror environment can be done in any order.
Still we recommend the following order:
1. Establish all necessary paths between the Global Copy primary LSSs and their
corresponding secondary LSSs. Here also, you may establish paths at the local site,
between the Master and any Subordinate storage disk subsystem LSSs, that will
participate in the Global Mirror session. When there is only one primary storage disk
subsystem involved, you do not need to define paths between the primary LSSs. In this
case, the communication between Master and Subordinate LSSs within the storage disk
subsystem is done internally.
2. Establish the Global Copy pairs between the A and B volumes. For this you use the
MODE(COPY) parameter option. You may wait until the first initial copy phase is complete
before continuing to the next step.
3. Establish FlashCopy relationships between the B and C volumes. Use the
MODE(ASYNC) parameter option with the corresponding TSO FCESTABL command.