IMS considerations

The following shows how AR/CTL supports IMS:

IMS requirements

If you are using AR/CTL for IMS (in a true IMS environment), your site must have a licensed copy of the IMS Database Manager. AR/CTL is supported for use with all IBM-supported versions and releases of IMS.

Note

When you migrate from one release of IMS to a new release, IMS requires all application programs to complete normally under the old release before executing under the new release. IMS cannot use a log data set created under a previous release during restart of a program on a new release.

AR/CTL product license

If a CPU authorization password to enable AR/CTL for IMS participation is not installed, AR/CTL does not participate in any IMS region. No IMS oriented services of AR/CTL are available, including the suspend-and-resume interface with BMC Software products for IMS.

PSB PROCOPTs

AR/CTL supports all PSB processing options (PROCOPTs) and DL/I databases.

Region types

IMS application programs use the same EXEC statement with AR/CTL as they use without AR/CTL. AR/CTL supports the following IMS region types:

DLI	IMS mode and IMS compatible mode
DBB	IMS mode and IMS compatible mode
BMP	IMS mode (AR/CTL supports BMPs running in an IMS DB/CTL environment.)

AR/CTL supports the EXEC DLI environment. AR/CTL also supports the use of IMS defined keywords that suppress checkpoint messages written to the operator console.

Automatic checkpoints

When the Automatic Checkpoints processing option is set to Y for an IMS program, AR/CTL saves the entire working storage area of the application program at each checkpoint performed. For programs (especially in a DLI batch environment) that have large working storage areas, consider the effect of writing the checkpoint records to the IMS logs and take appropriate action to prevent problems.

Fast Path databases

When an IMS application program accesses a Fast Path database, a final checkpoint must be performed before the dependent region terminates. Other checkpoints might be required in response to a status code from DL/I. Certain AR/CTL checkpoint/restart services can affect required checkpoints:

checkpoint pacing	Checkpoint pacing can cause a required checkpoint to be bypassed. Do not turn on checkpoint pacing unless you use the Checkpoint Pacing exit (force required checkpoints to be processed). Or you can change the calls in the application program to use the AR/CTL common call with the FORCE option.
automatic/checkpoint restart	When AR/CTL performs automatic checkpoint/restart for an application program, AR/CTL cannot determine when the application program is ready to terminate. Note Do not use automatic checkpoint/restart in an application program that accesses a Fast Path database.

Abend and restart on different IMS systems

AR/CTL supports application programs that abend on one IMS system and are restarted on another IMS system. The IMSID qualifier in the program registration record must contain wildcards.

Multiple MVS tasks

AR/CTL for IMS services must be invoked under the same task as the IMS region controller (DFSRRC00). Neither AR/CTL nor IMS can perform error recovery under a sibling or daughter task.