Script to see single wait per hour

I’ve taken a script I use to show a particular wait event over time and parameterized it a bit to make it more general.

Here is a zip of the script: zip(updated).

This is the same sort of information you see in an AWR report but just for one event and over all of the snapshots you have in your AWR.

Here is the main query:

(after.total_waits-before.total_waits) "number of waits",
(after.total_waits-before.total_waits) "ave microseconds",
before.event_name "wait name"
where before.event_name='&&WAITNAME' and
after.event_name=before.event_name and
after.snap_id=before.snap_id+1 and
after.instance_number=1 and
before.instance_number=after.instance_number and
after.snap_id=sn.snap_id and
after.instance_number=sn.instance_number and
(after.total_waits-before.total_waits) > &&MINIMUMWAITS
order by after.snap_id;

Here is a description of the two variables:

WAITNAME = Wait event like “log file sync”.

MINIMUMWAITS = Least amount of waits per hour to show that hour’s events.  Sometimes it is helpful to remove the hours where there isn’t much activity.

Here is some output with WAITNAME=log file sync and MINIMUMWAITS=100000:

END_INTERVAL_TIME          number of waits ave microseconds
-------------------------- --------------- ----------------
08-SEP-13 AM           194356       802.426964
08-SEP-13 AM           301482       705.784296
08-SEP-13 AM           162397       2736.56333
08-SEP-13 AM           333388       2380.95826
08-SEP-13 AM           439911       2469.45262
08-SEP-13 AM           697083        2847.4531
08-SEP-13 AM           744137       3424.96033
08-SEP-13 PM           731348       4022.53643
08-SEP-13 PM           674319       3691.63971
08-SEP-13 PM           748557        3108.9068

You can use this to identify changes in a waits average time and use an AWR report to do a deeper dive on any interval where you see something different from what is normal.

– Bobby

About Bobby

I live in Chandler, Arizona with my wife and three daughters. I work for US Foods, the second largest food distribution company in the United States. I have worked in the Information Technology field since 1989. I have a passion for Oracle database performance tuning because I enjoy challenging technical problems that require an understanding of computer science. I enjoy communicating with people about my work.
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5 Responses to Script to see single wait per hour

  1. Thushara says:

    Really a useful script and used it to find out the ‘log file synch’ event after we changed our DataGuard from MaxAvailability to Maxperformance.


  2. Pingback: Another python graph – one wait event | Bobby Durrett's DBA Blog

  3. kal says:

    Remove the IDLE WAIT
    and before.event_name not in (select name from SYS.V_$EVENT_NAME WHERE WAIT_CLASS = ‘Idle’)

    • Bobby says:

      Thanks for your comment! I think that in this script I am choosing which specific event to look at. So, I think that I am the one who decides whether the event is worth seeing instead of relying on the wait class to filter out events as not having value.

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