IBM 990 7.2 Sysplex and Coupling Facility considerations

Chapter 7. Sysplex functions 157

Draft Document for Review April 7, 2004 6:15 pm 6947ch07.fm

Through this state-of-the-art cluster technology, the power of multiple z/OS and/or OS/390

images can be harnessed to work in concert on common workloads. The zSeries Parallel

Sysplex cluster takes the commercial strengths of the z/OS or OS/390 platform to improved

levels of system management, competitive price/performance, scalable growth, and

continuous availability.

7.2 Sysplex and Coupling Facility considerations

Described here are the supported Parallel Sysplex configurations, required set-up information

when connected to an Sysplex Timer, different forms of Coupling Facilities (CFs) supported

on z990 servers, CFRM policy considerations and ICF processor assignments. The z990

models support both Central Processors (CPs) and Internal Coupling Facility (ICF)

processors.

The z990 family of servers does not provide a special model for a CF-only processor. You

can, however, have a z990 server with up to 16 PUs defined as ICFs.

Parallel Sysplex configurations today can have system images and Coupling Facilities located

across multiple servers. This can be anything from S/390 to zSeries servers. However, z990

brings some additional considerations to these types of configurations.

As server and Coupling Facility link technologies have improved over the years, the

synchronization tolerance between operating systems in a Parallel Sysplex has become more

rigorous. In order to ensure that any exchange of timestamped information between operating

systems in a sysplex involving the Coupling Facility observe the correct time ordering,

timestamps are now included in the message-transfer protocol between the server operating

systems and the Coupling Facility. This is known as Message Time Ordering.

Message Time Ordering requires a connection between the z990 CPC and the Sysplex Timer

whenever a Coupling Facility is located in a logical partition on a z990.

Therefore, when a Coupling Facility is configured as an ICF on any z990 model, the Coupling

Facility will require connectivity to the same 9037 Sysplex Timer that the systems in its

Parallel Sysplex are using for the time synchronization. If the ICF is on the same server as

one or more a member of its Parallel Sysplex, no additional Sysplex Timer connectivity is

required, since the server already has connectivity to the Sysplex Timer. However, when an

ICF is configured on any z990 model which does not host any systems in the same Parallel

Sysplex, it is necessary to attach the z990 server to the 9037 Sysplex Timer

Even though multiple servers can connect to only one Sysplex Timer unit, the typical

configuration is usually connected to two different Sysplex Timer units called an Expanded

Availability configuration. Refer to IBM^ zSeries Connectivity Handbook, SG24-5444,

for IBM 9037 Sysplex Timer connectivity information.

A Sysplex Timer unit is assigned a unique two-digit ID at installation time, called a Unit ID.

This Unit ID is referenced as an External Time Reference ID (ETR ID) in the output of the

z/OS command D ETR and Support Element panels.