Defining DBRC to IMS

You define DBRC to IMS as part of the IMS system definition process. This topic provides a brief overview of the requirements for creating and executing a DBRC region.

Related reading:

  • See Initializing and maintaining the RECON data sets for information on creating and allocating the RECON data set.
  • See Registering databases and database data sets for information about registering databases.
  • Refer to IMS Version 15 Installation, IMS Version 15 Release Planning, and IMS Version 15 System Definition for:
    • A complete description of the IMS installation procedures and requirements.
    • Information about the DBRC procedure and its parameters.
    • Information about the DFSIDEF0 module.
  • See IMS Version 15 Commands, Volume 3: IMS Component and z/OS Commands for detailed information about the INIT.RECON command.

IMS online systems always use DBRC; you cannot override this.

You can choose whether IMS batch jobs can use DBRC or not, but certain functions, such as data sharing, cannot be used without DBRC.

Batch and utility regions can use the DFSIDEF0 module during initialization. In DFSIDEF0, you can set the DBRC= keyword to YES, NO, or FORCE. The DFSIDEF0 module that is shipped in the ADFSSMPL library contains a batch and utility region default of DBRC=YES. This value is coded on the DFSIDEF macro.

Procedure

  1. Use the DBRCNM= parameter to request that IMS create a cataloged DBRC procedure.

    You can override the DBRC procedure name specified in your system definition in the DFSPBIMS, DFSPBDBC, and DFSPBDCC members.

  2. Determine whether DBRC is used in a batch procedure.

    If DBRC is going to be used in a batch procedure, specify this in the DBRC= EXEC parameter. This EXEC parameter is ignored by an online IMS.

    The DBRCNM= parameter can be used to override the DBRC procedure name for an online IMS execution.

  3. Place DBRC's load modules into a load library that is in the normal load library search sequence for your IMS load modules, for example, IMS.SDFSRESL.
  4. Include the DBRC procedure during system definition.

    IMS automatically starts the DBRC procedure by issuing a z/OS® START command during control region initialization. This procedure specifies parameters for the DBRC region. DBRC runs in its own address space for an online IMS subsystem.

    In IMS 15, the DBRC procedures are created during SMP/E processing in the IMS.SDFSPROC data set and should be copied to SYS1.PROCLIB. The member name must match the name specified on the DBRCNM parameter in the IMSCTRL macro or the applicable EXEC procedure.

    If DBRCNM is specified in more than one place, or if DBRCNM is not explicitly specified, the following order of precedence applies:

    • DBRCNM=DBRC is the default.
    • DBRCNM=name in the IMSCTRL macro overrides the default.
    • DBRCNM=name defined in a DFSPBxxx member in IMS.PROCLIB overrides the IMSCTRL macro setting.
    • DBRCNM=name defined in a JCL EXEC parameter overrides the IMS.PROCLIB member setting.
  5. Initialize the RECON data sets.

    Use the Access Method Services (IDCAMS) DEFINE CLUSTER command to create the RECON data sets and then use the INIT.RECON command to initialize the RECON data sets as usable by DBRC.

    If you do not intend to register databases, the INIT.RECON command is the only command you need to issue in order to initialize the data set.