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Dynamic connectivity to DB2 via Subzero

This implementation procedure offers the most flexibility. IMS and DB2 subsystems can be moved to different LPARs. Subzero makes the remote connections whenever necessary, and allows the local connections to occur whenever possible.

This implementation procedure requires the implementation of an IMS usermod, and subsequent stop and restart of IMS. It offers the following additional features:

  • You do not need to modify any IMS SSM member parameters. IMS SSM parameters are modified in real-time based upon Subzero definitions and DB2 subsystem availability.

  • IMS dependent regions can connect to DB2 Group Attach Names as well as specific DB2 Subsystems.

    For example, the IMS control region running on SYSA can connect to DB2B and DB2C running on SYSB and SYSC respectively. Assuming DB2B and DB2C are part of DB2 Group DB2G, the IMS dependent regions can specify an SSM member with a SSN=DB2G in order to establish a remote connection to an available DB2 subsystem on SYSB or SYSC.

  • IMS can connect to local DB2 subsystems using native interfaces and remote DB2 subsystems using Subzero.

    For example, IMSA on SYSA may have a SSN=DB2B definition.

    If DB2B is running on SYSB, Subzero will make the remote connection without the use of any native DB2 interfaces.

    If DB2B is running on SYSA, Subzero will simply pass the connection to the native DB2 interface routines without any further execution of Subzero code.

The IMS usermod front-ends the IBM SSM member edit routine (DFSESI00) and performs a real-time scan of the Sysplex for DB2 subsystems. When running inside the IMS control region, the Subzero front-end looks for the individual DB2 subsystems on the local LPAR. If found, the SSM member parameter is not modified for that DB2 connection. If the DB2 subsystem is found on a remote LPAR and there is a Subzero definition for it, the Subzero front-end routine will modify the in-core SSM member parameter data to enable the Subzero initialization table (BRDMIN10) to make the remote connection to DB2.

When running inside the IMS dependent regions, the Subzero SSM member edit routine scans the remote connection table to find any remote DB2 subsystems. If one is found, Subzero will again, modify the in-core SSM member parameter data to enable the Subzero initialization table. If the IMS dependent region SSM member data specifies a DB2 Group Attach Name, Subzero will look for a remote DB2 subsystem within that group. If found, it will alter the in-core SSM member parameter data to connect to the specific DB2 Subsystem. Like IMS, Subzero will find the first available DB2 subsystem within the DB2 group and make the remote connection.

To create a dynamic connection to DB2 via Subzero

  1. Apply the IMS usermod:
    1. Edit the usermod - BRDSMP01. It can be found in SAMPLIB.Modify the following elements as instructed within the JCL:
      • Subzero high-level qualifier
      • IMS Distribution load library
      • IMS RESLIB
      • IMS SMP/E CSI
      • IMS SMP/E Target Zone
      • Modify the ++VER to specify only the entry for the correct IMS version

    2. Run the job. By default, this does an APPLY CHECK of the usermod. If the APPLY CHECK is successful, you can remove the CHECK parameter and rerun the job.

      Warning

      Note

      Do not accept this usermod. Reject this usermod before applying IMS maintenance and then re-apply the usermod afterwards.

  2. Change your IMS startup JCL:

    1. Add the Subzero product library to the DFSESL statement in your IMS Control Region JCL.
    2. Add the Subzero product library to the DFSESL DD statement in your IMS Dependent Region JCL.
    Warning

    Note

    You do not need to remove any DB2 load libraries however, they are not needed for remote DB2 connectivity and can be removed unless there are application program requirements for them to be present (e.g. DSNTIAR to format messages).

  3. Stop and re-start IMS.

  4. Look for BRD0022I and BRD0023I messages indicating that remote subsystem connectivity is available. For example:BMCBRD0023I BMC Subsystem Optimizer for zEnterprise IMS initialized by subsystem AXL2

    BMCBRD0022I BMC Subsystem Optimizer for zEnterprise is active for remote DB2 connections
     

  5. Look for BRDM001 and/or BRD0150I messages indicating that your DB2 Subsystem connections are started and being redirected by Subzero. For example:BMCBRD0150I Redirecting T2HZ to DB2 DEHZ on system SYSM

    BRDM001I IMS/TM T13P CONNECTED TO SUBSYSTEM T2HZ

Related topic

Configuring-IMS-to-communicate-with-DB2



 

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Subsystem Optimizer 3.1