Designing a mixed complex (sysplex does not match complex)

As stated earlier, a global resource serialization complex consists of all the systems that are able to share global resources. There are links between the systems that enable them to communicate, primarily by passing the RSA-message from one system to another. Each system in the complex indicates at IPL time that it is to be part of the complex.

You need to decide how many of these systems to combine into one complex. The design of global resource serialization allows up to 32 systems per complex. However, the practical limit is much lower. The actual number of systems your particular installation can reasonably configure into a complex depends on a number of factors. You should, for example, consider the operations and performance implications of a very large complex.

Note: Global resource serialization ring complexes can contain XCFLOCAL, MONOPLEX, or systems that are part of a multisystem sysplex. However, only one multisystem sysplex can exist in any global resource serialization complex.

Once you have selected the systems that are to be part of the complex, you must then define the communication links that connect the systems. Use the information in Choosing the link configuration to help you with this process. Since systems outside of a sysplex cannot communicate using XCF, you must provide communication links that global resource serialization can use. Use the information in Choosing the link configuration to help you with this process.

Choosing the link configuration is one major part of designing a mixed complex; the other is defining the processing options that your complex needs. For example, you must decide:

The length of the residency time value, that is, the minimum length of time a system is to hold the RSA-message before sending it on to the next system in the ring.
The length of the tolerance interval, that is, the maximum length of time that global resource serialization is to wait for the incoming RSA-message before it signals a disruption.
Whether or not the system can automatically rebuild a disrupted global resource serialization ring.
Whether or not the system can automatically rejoin the ring after it has temporarily stopped.
Whether or not to use ring acceleration, and if so, the number of systems in the ring that need to know about global resource requests before they can be granted.

Use the information in Processing options in a mixed complex to make these decisions.

Planning aids

Defining the complex to MVS includes a blank configuration diagram and a worksheet for recording the design of your complex. The diagrams and worksheet can help you implement your plan.

Reference

Once you have completed your plan, see z/OS MVS Initialization and Tuning Reference for information about how to specify the global resource serialization parmlib member and system parameters.