For remote file control or temporary storage requests shipped over IPIC connections, CICS will no longer force a switch to the QR TCB in the Application Owning Region (AOR) if it’s currently running on an open TCB. The requests will be shipped running on the open TCB.

In the FOR or Queue Owning Region (QOR), the mirror decides when to switch to an open TCB. It does so for the first file control or temporary storage request received over an IPIC connection. The idea is for long-running mirrors to keep the mirror running on an open TCB.

A new option, MIRRORLIFE, was added to the IPCONN attributes for function-shipped file control and temporary storage requests using an IPIC connection. MIRRORLIFE improves efficiency and provides performance benefits by specifying the lifetime of mirror tasks and the amount of time a session is held.

Threadsafe CICS-DBCTL Interface

CICS provides a CICS-IMS Database Control (CICS-DBCTL) interface to support CALL DLI and EXEC DLI requests issued by applications running in a CICS region. In CICS TS 4.2, the CICS-DBCTL interface was enhanced to exploit OTE; CICS can run the CICS-DBCTL Task Related User Exit (TRUE) on an L8 open TCB.

OTE is supported from IMS Version 12 with Program Temporary Fixes (PTFs) for APARs PM31420, PM45414, and PM47327 applied. IMS indicates to CICS during the connection process that the OTE is supported. Consequently, CICS defines the CICS-DBCTL TRUE as an OPENAPI TRUE. For IMS Version 11 and earlier, OTE isn’t supported and CICS runs the CICS-DBCTL TRUE on the QR TCB and the IMS code switches to an IMS thread TCB.

Running an application on an open TCB improves throughput and performance by reducing the use of the QR TCB. Threadsafe CICS applications that run on an L8 open TCB and issue CALL DLI or EXEC DLI commands can avoid two TCB switches for each call to IMS.

For a non-threadsafe application, there’s no reduction in the amount of switching. Instead of switching from the QR TCB to an IMS thread TCB and back again for each IMS request, the application switches from QR to L8 and back again.

For a threadsafe application, if it’s running on the QR TCB, it switches to L8 and then stays on L8 when control is returned to the application.

For a threadsafe application that’s already running on an L8 TCB, or for a CONCURRENCY(REQUIRED) application that’s running on an L8 TCB, no TCB switching occurs for the IMS request.

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