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    DB time in AWR "Instance Activity Stats" section

    1007800
      Dear all,

      I don't understand in what metric this db time metric is expressed. Is it in milli-, micro-, centiseconds?
      I have 3,848.36 dbtime per second but what does that mean in seconds?

      Instance Activity Stats

      Statistic     Total     per Second     per Trans
      CPU used by this session      78,259      21.76      60.53
      CPU used when call started      188,815      52.51      146.03
      CR blocks created      1,628      0.45      1.26
      Cached Commit SCN referenced      3,492,204      971.18      2,700.85
      Commit SCN cached      63,550      17.67      49.15
      DB time      13,838,024      +3,848.36+      10,702.26

      Kind regards,

      Jorn

      Edited by: 1004797 on May 8, 2013 7:14 AM
        • 1. Re: DB time in AWR "Instance Activity Stats" section
          asahide
          Hi,

          These links may help you..
          <<http://oracledoug.com/serendipity/index.php?/archives/1429-Time-Matters-DB-Time.html>>
          <<http://asktom.oracle.com/pls/apex/f?p=100:11:0::NO::P11_QUESTION_ID:229943800346471782>>


          Regards,
          • 2. Re: DB time in AWR "Instance Activity Stats" section
            1007800
            Thanks but i know what db time is but the problem is the metric(seconds, millisecond,...) is never expressed behind the figure... and that just doesnt make sense...
            • 3. Re: DB time in AWR "Instance Activity Stats" section
              Dom Brooks
              DB Time is a great metric but I would usually refer to it in the top level summary, the load profile and the time model statistics.

              It refers to the time spent by foreground sessions actively waiting or actively working.

              In a one hour period, if there is one session constantly working, the DB time would be 1 hour.
              If there are two sessions constantly working, then DB time would be 2 hours, etc.

              Regarding the difference between values in the different sections, the DB time in the instance activity stats looks to be centiseconds and rounding errors and/or different collection intervals might account for the difference.
              • 4. Re: DB time in AWR "Instance Activity Stats" section
                1007800
                Hi,

                Thanks for you reply but that would mean i have worked 38.4836seconds in 1 second with only 14 cores.

                Regards
                • 5. Re: DB time in AWR "Instance Activity Stats" section
                  Dom Brooks
                  Perfectly possible.
                  Sounds like you're confusing DB time with CPU time.
                  Cores are irrelevant.

                  If in doubt, see your load profile.

                  DB time represents Average Active Sessions in a time period.

                  In a 1 second period....
                  If for 100% of that 1 second period, you have 1 session either on cpu or waiting for cpu or actively waiting for a non idle event, DB time is 1 second.
                  If for 100% of that 1 second period, you have 2 sessions either on cpu or waiting for cpu or actively waiting for a non idle event, DB time is 2 seconds.
                  If for 100% of that 1 second period, you have 5 sessions either on cpu or waiting for cpu or actively waiting for a non idle event, DB time is 5 seconds.
                  If for 100% of that 1 second period, you have 38 sessions either on cpu or waiting for cpu or actively waiting for a non idle event, DB time is 38 seconds.

                  To a certain extent, it doesn't matter if I double the number of cores or halve the number of cores, if I have 38 sessions actively working or actively waiting for 100% of that 1 second, then DB time for that 1 second is 38 seconds.
                  • 6. Re: DB time in AWR "Instance Activity Stats" section
                    1007800
                    Dear,

                    Thank you for the brief explanation.

                    Ok I understand cores haven't got much to do with db time. But that doesn't really answer my question.
                    So in the Instance Activity Stats section of the AWR report there is a metric called db time. In what is that value expressed?
                    In below example is this 3,848.36 seconds per second? or is it 3,848.36 milliseconds or centi-seconds or...

                    Instance Activity Stats

                    Statistic     Total     per Second     per Trans
                    CPU used by this session      78,259      21.76      60.53
                    CPU used when call started      188,815      52.51      146.03
                    CR blocks created      1,628      0.45      1.26
                    Cached Commit SCN referenced      3,492,204      971.18      2,700.85
                    Commit SCN cached      63,550      17.67      49.15
                    DB time      13,838,024      3,848.36      10,702.26

                    Thanks in advance
                    • 7. Re: DB time in AWR "Instance Activity Stats" section
                      Aman....
                      Even in the example of Dom, it's clearly mentioned that it's going to be in seconds.

                      Aman....
                      • 8. Re: DB time in AWR "Instance Activity Stats" section
                        1007800
                        Ok THX!

                        1 other thing.
                        If the "Total" db time= 13,838,024 seconds and the "per Second" = 3,848.36 (seconds if i believe this topic) why then I need to calculate 13,838,024/60/60 to become 3843,895556?

                        Thanks for the info!

                        Regards,

                        J.
                        • 9. Re: DB time in AWR "Instance Activity Stats" section
                          Dom Brooks
                          I mentioned in my original reply that the unit of measurement for DB Time in the instance activity stats section is centiseconds.
                          • 10. Re: DB time in AWR "Instance Activity Stats" section
                            1007800
                            I agree Dom,

                            But if in this example its 13,838,024 centiseconds total db time how do I then get to 3,848.36 per seconds. I'm just trying to figure out how these figures correlate to each other...

                            Regards,

                            J

                            Edited by: 1004797 on May 13, 2013 1:54 AM
                            • 11. Re: DB time in AWR "Instance Activity Stats" section
                              Dom Brooks
                              Different metrics can be captured in slightly different ways and/or at slightly different intervals plus you get rounding errors.

                              But what's the exact duration of the AWR report?
                              • 12. Re: DB time in AWR "Instance Activity Stats" section
                                1007800
                                Dom,

                                The duration is 1hr of the awr report.

                                regards,

                                J

                                Edited by: 1004797 on May 13, 2013 5:10 AM
                                • 13. Re: DB time in AWR "Instance Activity Stats" section
                                  Dom Brooks
                                  But if in this example its 13,838,024 centiseconds total db time how do I then get to 3,848.36 per seconds. I'm just trying to figure out how these figures correlate to each other..
                                  The duration is 1hr of the awr report.
                                  Probably more like 59.93 minutes...

                                  It should be that

                                  13,838,024 / Exact duration of the AWR report in seconds = Average DB time per second
                                  • 14. Re: DB time in AWR "Instance Activity Stats" section
                                    1007800
                                    Dear Dom,

                                    Thanks a lot. It's getting a lot clearer for me :-)
                                    So on average my db works 3843 dbtime centi seconds per second in this interval.

                                    Thx a lot for the clarification!

                                    Edited by: 1004797 on May 13, 2013 6:22 AM
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