Comparing a Baseline to Another Baseline or Pair of Snapshots

When performance degradation occurs over time, you can run the AWR Compare Periods report to compare the degraded performance, captured as a new baseline or a pair of snapshots, to an existing baseline. You must have a baseline that represents the system operating at an optimal level. If an existing baseline is unavailable, then compare database performance between two periods of time using two arbitrary pairs of snapshots, as described in "Comparing Two Pairs of Snapshots".

To compare a baseline to another baseline: 

1. From the Database Home page, click Server.

   The Server subpage appears.

2. Under Statistics Management, click Automatic Workload Repository.

   The Automatic Workload Repository page appears.

3. Under Manage Snapshots and Baselines, click the link next to Baselines.

   The AWR Baselines page appears.

4. Complete the following steps:

   1. Select the baseline to use for the report.

      At least one existing baseline must be available.

   2. From the Actions list, select Compare Periods and click Go.

   The Compare Periods: Second Period Start page appears. Under First Period, the selected baseline is displayed.

5. Compare the baseline selected in the first period to another baseline or a pair of snapshots. Do one of the following:

   • To compare to another baseline, select Select a Baseline and the baseline you want to use in the second period, and then click Next.

     The Compare Periods: Review page appears. Go to Step 7.

   • To compare to a pair of snapshots, select Select Beginning Snapshot and the beginning snapshot to use in the second period, and then click Next.

     The Compare Periods: Second Period End appears. Proceed to the next step.

6. Select the ending snapshot for the snapshot period that will be included in the report and then click Next.

   The Compare Periods: Review page appears.

7. Review the periods to be included in the report and then click Finish.

   The Compare Periods: Results page appears.

   Data from the selected periods appears under the General subpage. You can view data per second or per transaction by selecting an option from the View Data list.

   Note: If the time periods have different lengths, then the data is normalized over database time before calculating the difference so that periods of different lengths can be compared.

8. Click Report to view the report.

   The Processing: View Report page appears while the report is being generated. After it completes, the report will appear. To change periods, click Change Periods. To save the report as an HTML file, click Save to File.

9. Optionally, do the following:

   • To change periods, click Change Periods.

   • To save the report as an HTML file, click Save to File.