How to manage Activation Groups - IBM - RPG

An activation group is a substructure of a job and consists of system resources (for example, storage, commitment definitions, and open files) that are allocated to run one or more ILE or OPM programs. Activation groups make it possible for ILE programs running in the same job to run independently without intruding on each other (for example, commitment control and overrides). The basic idea is that all programs activated within one activation group are developed as one cooperative application.

You identify the activation group that your ILE program will run in at the time of program creation. The activation group is determined by the value specified on the ACTGRP parameter when the program object was created. (OPM programs always run in the default activation group; you cannot change their activation group specification.) Once an ILE program (object type *PGM) is activated, it remains activated until the activation group is deleted.

The remainder of this section tells you how to specify an activation group and how to delete one. For more information on activation groups, refer to ILE Concepts.

Specifying an Activation Group
You control that activation group your ILE program will run in by specifying a value for the ACTGRP parameter when you create your program (using CRTPGM or CRTBNDRPG) or service program (using CRTSRVPGM).

Note: If you are using the CRTBNDRPG command, you can only specify a value for ACTGRP if the value of DFTACTGRP is *NO.

You can choose one of the following values:

• a named activation group
  A named activation group allows you to manage a collection of ILE programs and service programs as one application. The activation group is created when the first program that specified the activation group name on creation is called. It is then used by all programs and service programs that specify the same activation group name. A named activation group ends when it is deleted using the CL command RCLACTGRP. This command can only be used when the activation group is no longer in use. When it is ended, all resources associated with the programs and service programs of the named activation group are returned to the system. The named activation group QILE is the default value of the ACTGRP parameter on the CRTBNDRPG command. However, because activation groups are intended to correspond to applications, it is recommended that you specify a different value for this parameter. For example, you may want to name the activation group after the application name.
• *NEW
  When *NEW is specified, a new ativation group is created whenever the program is called. The system creates a name for the activation group. The name is unique within your job.An activation group created with *NEW always ends when the program(s) associated with it end. For this reason, if you plan on returning from your program with LR OFF in order to keep your program active, then you should not specify *NEW for the ACTGRP parameter.*NEW is the default value for the ACTGRP parameter on the CRTPGM command.If you create an ILE RPG program with ACTGRP(*NEW), you can then call the program as many times as you want without returning from earlier calls. With each call, there is a new copy of the program. Each new copy will have its own data, open its files, etc.. However, you must ensure that there is some way to end the calls to ’itself’;otherwise you will just keep creating new activation groups and the programs will never return.
• *CALLER
  The program or service program will be activated into the activation group of the calling program. If an ILE program created with ACTGRP(*CALLER) is called by an OPM program, then it will be activated into the OPM default activation group
  (*DFTACTGRP).

Running in the OPM Default Activation Group
When an OS/400 job is started, the system creates an activation group to be used by OPM programs. The symbol used to represent this activation group is *DFTACTGRP. You cannot delete the OPM default activation group. It is deleted by the system when your job ends.

OPM programs automatically run in the OPM default activation group. An ILE program will also run in the OPM default activation group when one of the following occurs:

• The program was created with DFTACTGRP(*YES) on the CRTBNDRPG command.
• The program was created with ACTGRP(*CALLER) at the time of program creation and the caller of the program runs in the default activation group. Note that you can only specify ACTGRP(*CALLER) on the CRTBNDRPG command if DFTACTGRP(*NO) is also specified.

Note: The resources associated with a program running in the OPM default activation group via *CALLER will not be deleted until the job ends.

Maintaining OPM RPG/400® and ILE RPG Program Compatibility
If you have an OPM application that consists of several RPG programs, you can ensure that the migrated application will behave like an OPM one if you create the ILE application as follows:

1. Convert each OPM source member using the CVTRPGSRC command, making sure to convert the /COPY members. See “Converting Your Source” for more information.
2. Using the CRTBNDRPG command, compile and bind each converted source member separately into a program object, specifying DFTACTGRP(*YES).

Deleting an Activation Group
When an activation group is deleted, its resources are reclaimed. The resources includestatic storage and open files. A *NEW activation group is deleted when the program it is associated with returns to its caller.

Named activation groups (such as QILE) are persistent activation groups in that they are not deleted unless explicitly deleted or unless the job ends. The storage associated with programs running in named activation groups is not released until these activation groups are deleted.

An ILE RPG program created DFTACTGRP(*YES) will have its storage released when it ends with LR on or abnormally.

Note: The storage associated with ILE programs running in the default activation group via *CALLER is not released until you sign off (for an interactive job) or until the job ends (for a batch job).

If many ILE RPG programs are activated (that is called at least once) system storage may be exhausted. Therefore, you should avoid having ILE programs that use large amounts of static storage run in the OPM default activation group, since the storage will not be reclaimed until the job ends.

The storage associated with a service program is reclaimed only when the activation group it is associated with ends. If the service program is called into the default activation group, its resources are reclaimed when the job ends.

You can delete a named activation group using the RCLACTGRP command. Use this command to delete a nondefault activation group that is not in use. The command provides options to either delete all eligible activation groups or to delete an activation group by name.

Reclaim Resources Command
The Reclaim Resources (RCLRSC) command is designed to free the resources for programs that are no longer active. The command works differently depending on how the program was created. If the program is an OPM program or was created with DFTACTGRP(*YES), then the RCLRSC command will close open files and free static storage.

For ILE programs or service programs that were activated into the OPM default activation group because they were created with *CALLER, files will be closed when the RCLRSC command is issued. For programs, the storage will be re-initialized; however, the storage will not be released. For service programs, the storage will neither be re-initialized nor released.

Note: This means that if you have a service program that ran in the default activation group and left files open (returning with LR off), and a RCLRSC is issued, when you call the service program again, the files will still appear to be open, so so any I/O operations will result in an error.

For ILE programs associated with a named activation group, the RCLRSC command has no effect. You must use the RCLACTGRP command to free resources in a named activation group.