One-phase commit global transactions with IMS TM Resource Adapter

If only one resource manager is registered in a transaction that is making changes to shared resources, the transaction manager can perform one-phase-commit optimization. An external coordinator is not required.

The transaction manager can send the phase two commit request directly to the resource manager to commit the changes. IMS Connect does not have to go through phase one, prepare to commit of the two-phase commit protocol and can go directly to phase two, commit request.

If support for cascading global transactions is enabled by the specification of CASCADE=Y in either the IMS Connect system configuration or IMS Connect data store definitions, IMS Connect and IMS can process a global transaction when IMS Connect and IMS are each running on different z/OS® images. When support for cascading global transactions is disabled, IMS Connect, RRS, and IMS must all be on the samez/OS image.

The following figure illustrates the flow for a distributed one-phase commit global transaction.

Figure 1. Distributed one-phase commit optimization client flow
begin figure description. An illustrated diagram showing the client flow for a distributed two-phase commit local transaction which involves an application server, IMS Connect, RRS, and an IMS. end figure description.