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GDPS is discussed in a white paper available at ibm.com/
server/eserver/zseries/pso/library.html. GDPS is a service
offering of IBM Global Services. For IBM Installation Ser-
vices for GDPS, refer to the IBM Web site.
Message Time Ordering (Sysplex Timer Connectivity to Coupling
Facilities)
As processor and Coupling Facility link technologies have
improved over the years, the requirement for time synchro-
nization tolerance between systems in a Parallel Sysplex
environment has become ever more rigorous. In order to
enable that any exchanges of timestamped information
between systems in a sysplex involving the Coupling Facil-
ity observe the correct time ordering, time stamps are now
included in the message-transfer protocol between the sys-
tems and the Coupling Facility. Therefore, when a Coupling
Facility is confi gured as an ICF on any z890, z990 or z900
Models 2C1 through 216, the Coupling Facility will require
connectivity to the same 9037 Sysplex Timer that the sys-
tems in its Parallel Sysplex cluster are using for time syn-
chronization. If the ICF is on the same server as a member
of its Parallel Sysplex environment, no additional connectiv-
ity is required, since the server already has connectivity to
the Sysplex Timer. However, when an ICF is confi gured on
any z890, z990 or z900 Models 2C1 through 216 which do
not host any systems in the same Parallel Sysplex cluster, it
is necessary to attach the server to the 9037 Sysplex Timer.
Continuous Availability Recommended Confi guration for Parallel
Sysplex
Note: z890/z990 will attach to 9037-001 or 9037-002. Ser-
vice for 9037-001 discontinued end of 2003.
Components and assumptions
• Two Coupling Facilities; at least one external or else
using System-Managed CF Structure Duplexing
• Two Sysplex Timers
• Two z/OS or OS/390 servers with redundant backup
capacity
• Two links from each CF to each image
• Two hardware management consoles
• Two ESCON or FICON Directors with cross-connected
disks
• Dual electrical power grids
• Cloned OS/390 images, latest available software levels
• Automation capabilities for recovery/restart
• Critical data on RAID and/or mirrored disks
z900 Turbo or z890/z990 Model with ICF
and non-Parallel Sysplex LPARs
z/OS
Non-Sysplex
LPARs
CF01
ICF
z/OS
CF02
ICF
z/OS
IBM ^ z900
or z890/z990
Sysplex
LPARs
CF02
ICF
IC
IBM ^ z900
or z890/z990
Sysplex
LPARs
New Connection to Sysplex Timer
New Connection to Sysplex Timer
ICB-3/ ICB-4 / ISC-3
ICB-3 / ICB-4/ ISC-3
1
12
2
3
4
5
6
7
8
9
10
11
1
12
2
3
4
5
6
7
8
9
10
11
Sysplex Timers
ESCON/FICON Express Channels
z/OSz/OS
Internal Coupling
Facility
Dedicated (External)
Coupling Facility
ICF
IC
z890 or
z990 with
CFs only,
z900 Model 100
9674, 9672 R06,
or z800 Model 0CF