Updating subsystem parameter and application default values

You can dynamically update the value of some subsystem parameters while Db2 is running. For other subsystem parameters, you must stop and restart Db2 to change the values.

Before you begin

Important: Changes to subsystem parameters affect the entire subsystem. Carefully evaluate and plan for the impact of any changes to these values. Also, follow any advice that is included in the documentation for the parameter.

Determine whether you will update the subsystem parameters values online or offline. Not all parameters can be updated online. To check whether a particular subsystem parameter can be updated online, see Directory of subsystem parameters, panel fields, and application default values.

To change the following security-related subsystem parameters, the privilege set of the process must include installation SYSADM authority or SECADM authority:

About this task

Restriction: The following procedure cannot be used for some subsystem parameters that define characteristics of the Db2 catalog, directory, BSDS, and logs or for the DDF subsystem parameter. For these parameters, follow the instructions in Updating subsystem parameters that cannot be updated by using DSNTIPB.

Procedure

Begin general-use programming interface information.To update subsystem parameter values, complete the following steps:

  1. Invoke the CLIST:
    1. Check that your TSO logon region size is sufficient.
      Usually 2 MB is enough.
    2. Invoke ISPF.
    3. Select option 6 on the main ISPF panel.
    4. Run the Db2 installation CLIST by entering one of the following specifications: 
      • EXEC 'prefix.SDSNCLST(DSNTINST)'
      • If you want to receive the messages that trace the progress of the CLIST, use the following specification:
        EXEC 'prefix.SDSNCLST(DSNTINST)' 'CONTROL(LIST)'
      • If you want to use the CLIST but skip the verification of output data sets, use the following specification:
        EXEC 'prefix.SDSNCLST(DSNTINST)' 'CHKOUTDS(NO)'
        By default, the CLIST verifies the following information when installation panels DSNTIPT and DSNTIPA1 are displayed:
        • The CLIST verifies that the TEMP CLIST LIBRARY and SAMPLE LIBRARY that you specify on DSNTIPT can be allocated and opened for output.
        • If you specify a value for OUTPUT MEMBER NAME on DSNTIPA1, the CLIST verifies that the data set prefix.SDSNSAMP can be allocated and opened for output.
    The CLIST reads a set of default values and displays them on the panels. The values can be the original default values that are supplied by IBM®, values that you specified in a previous run of the CLIST, or values that were generated when you ran the DSNTXAZP tool.
  2. On installation panel DSNTIPA1, in field 1 INSTALL TYPE, specify UPDATE and press Enter.
  3. On installation panel DSNTIPT, in field 2 SAMPLE LIBRARY, specify the output SDSNSAMP data set and press Enter.
    Panel DSNTIPB is displayed.
  4. On panel DSNTIPB, specify the installation panel that you want to update and press Enter.
  5. Change the values on the panel as needed, and press Enter to return to panel DSNTIPB.
  6. Optional: Repeat steps 4 - 5 until you specify all of the updates that you want.
  7. On panel DSNTIPB, press ENTER again to complete the update process.

    Start of changeDepending on the values that you change, this process produces any of the following jobs with the new values: DSNTIJUZ, DSNTIJUA, and DSNITJUL.End of change

    The default SQL processing level (SQLLEVEL) for the precompiler/coprocessor can be changed anytime, such as after activating a higher Db2 function level. For more information, see PRECOMPILER SQL LEVEL field (SQLLEVEL DECP value).
    Important: With the exception of SQLLEVEL, updates to application defaults parameters are generally not recommended. In general, you must restart Db2 for changes to any application programming parameters to take effect.
    For updates, the Db2 installation CLIST generates job DSNTIJUL only for changes to any of the following parameters:

    This process produces a new DSNTIJUZ job with the new values; it also saves these values in the file that is specified in the OUTPUT MEMBER NAME field on panel DSNTIPA1. For more information, see OUTPUT MEMBER NAME field.

  8. Run job DSNTIJUZ.
    Job DSNTIJUZ defines the Db2 data-only subsystem parameter module (DSNZPxxx), which consists of the expansion of the following macros: DSN6ARVP, DSN6FAC, DSN6GRP, DSN6LOGP, DSN6SPRM, and DSN6SYSP.
    You might need to make the following adjustments before running the job:
    • If you added a STEPLIB DD statement to the Db2 start procedures ahead of prefix.SDSNEXIT and prefix.SDSNLOAD, you can move the SYSLMOD output to that library.
    Important: Start of changeIf the DSNTIJUZ job ends with return code 4, check that any warning messages can be safely ignored before continuing to the next step.End of change
    When DSNTIJUZ completes, the DSNTINST CLIST performs calculations by using the values that you specified for some of the parameter values that you entered on the panels. These calculations appear in the macro descriptions.

    For more information, see Job DSNTIJUZ: define the Db2 data-only subsystem parameter module.

  9. Start of change If you modified application programming default values, run the generated DSNTIJUA job.
    Job DSNTIJUA defines the Db2 data-only application defaults module.
    You might need to make the following adjustments before running the job:
    • If you added a STEPLIB DD statement to the Db2 start procedures ahead of prefix.SDSNEXIT and prefix.SDSNLOAD, you can move the SYSLMOD output to that library.

    For more information, see Job DSNTIJUA: define data-only application defaults module.

    End of change
  10. Start of change If the CLIST generated the DSNTIJUL job when you completed step 7, run job DSNTIJUL.
    Job DSNTIJUL runs the Db2 change log inventory (DSNJU003) to update DDF-related information in the BSDS. For more information, see Job DSNTIJUL: update DDF related BSDS information.
    End of change
  11. Use one of the following methods to tell the subsystem to begin using the new load module:
    • For online updates, issue the SET SYSPARM command: 
      SET SYSPARM LOAD(load-module-name)
      where load-module-name is the same as the OUTPUT MEMBER NAME field value that was specified on the DSNTIPA1 panel.

      If you want to specify the load module name that is used during Db2 startup, you can issue the following command: 

      SET SYSPARM RELOAD
    • For offline updates, stop and restart Db2 with the new subsystem parameter load module.End general-use programming interface information.