Manually resolving access path regressions

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Follow this process to manually resolve access path regressions.

About this task

IBM® Z Database Assistant provides options for handling access path regressions if they occur.

If you do not select Automatically resolve all regressions in the access path regression settings, you might need to manually resolve some regressions. For more information about access path regressions settings, see Updating SQL tuning settings.

Procedure

To analyze detected regression:

  1. Open the SQL tuning tab of the connection for which you want to improve SQL performance.
  2. Click the Regression detection tab.
  3. Click View details in the Actions column to view access path performance comparison details.
    The result field above the table indicates if there was regression and the weighted delta %.

    The confidence % indicates the degree of confidence that IBM Z Database Assistant has in the weighted delta percent. It indicates confidence that the Weighted delta % is accurate. It can vary between 0% (lowest possible confidence) and 99% (highest possible confidence).

    You can use these details to determine if you want to resolve or skip the detected regression. For more information about manually resolving access path regression, see Manually resolving access path regressions.

  4. Close the access path performance details panel.

To resolve access path regression:

  1. Select the checkbox next to the statement name.
  2. Click Resolve.
    This opens the Resolve regressions dialog.
  3. Select the Rebind packages checkbox to rebind the package containing the statement. This is necessary for the regression resolution to take effect.
    The checkbox is selected by default. If you do not choose this option, you will need to perform a rebind separately.
  4. Select the Resolve immediately checkbox to immediately complete the steps necessary to resolve the regression.
    The checkbox is selected by default. If you do not choose this option, the Resolution scheduler appears.
    1. If you choose not to resolve immediately, specify the following values:
      Resolve label
      An optional user-defined descriptor for a particular regression resolution schedule.
      Kick-off date and time
      The date and time when the regression resolution will begin.
      Max end date and time
      The date and time at which a regression resolution will end if it has not finished already.
    2. Click Resolve.

To skip an access path recommendation:

  1. Select the checkbox next to the statement name.
  2. Click Skip.
    This opens the Resolve regressions dialog.
  3. Click Skip.