IMSPLEX Execution Considerations

There are many reasons for the re-emergence of the mainframe as a viable processing platform. Probably the most important reason of all, however, was IBM's* decision to enable IMS for MVS Parallel Sysplex. The MVS Parallel Sysplex provides an easily scalable computing platform, which is more cost-efficient than the historical mainframe environment. Parallel Sysplex also provides an environment where 24x7 can be more readily achieved.

The connection of two or more IMS systems in a Parallel Sysplex is commonly referred to as an IMSPLEX. Enhancements introduced in previous releases of IMS provide two main capabilities of the IMSPLEX: data sharing and workload sharing.

IMS V5 was the first release to be enabled for Parallel Sysplex. IMS databases can now be shared at the block level across as many as 255 IMS subsystems. The data may be read and updated by the IMS systems participating in the data sharing. This capability of the IMSPLEX is referred to as N-way data sharing. The set of IMS systems involved in this type of IMSPLEX is referred to as a data-sharing group. The sharing of database records is accomplished using lock and cache structures residing in the coupling facility. The IMS Resource Lock Manager (IRLM) address space provides the necessary serialization.

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