Re: Instrumenting Poor performance

Hi Upendra

I see that you say that this occurs around the start of each month and disappears after a couple of days. Have you perhaps partitioned your Order Entry tables and (assuming the plan really is the same) you are starting to access new partitions for the first time? Usually month change funniness would involve getting a plan change from/to nested loop access to the data as a result of misleading stats on the new partition, but I see no reason in principle why there wouldn't be a caching effect - though I'd be surprised if it lasted days.

On Mon, Sep 17, 2018 at 10:27 PM Upendra nerilla <nupendra_at_hotmail.com> wrote:

> Dominic/Jonathan/Stefan and others,
> Aplogies for the delay... I was trying to make sure I go back and review
> all the data that we already have gathered..
>
> A couple of quick information:
> This is running from EE 12.1.0.2 RAC.
> We do have Tuning/Diag licenses.
>
> It turns out, we do have a bit of useful information gathered during our
> last poor execution..
>
> 1. We have the 10046 trace
> 2. SQLT report
>
> I performed a quick profiler comparison for both the bad and good
> execution, plan hash is the same. Here is the summary of the tkprof out how
> it appears..
>
> Bad run:
> call count cpu elapsed disk query current
> rows
> ------- ------ -------- ---------- ---------- ---------- ----------
> ----------
> Parse 0 0.00 0.00 0 0 0
> 0
> Execute 3 0.00 0.00 0 0 0
> 0
> Fetch 3 160.44 1289.07 3673632 13274897 0
> 368
> ------- ------ -------- ---------- ---------- ---------- ----------
> ----------
> total 6 160.44 1289.07 3673632 13274897 0
> 368
>
>
> Good run:
> call count cpu elapsed disk query current
> rows
> ------- ------ -------- ---------- ---------- ---------- ----------
> ----------
> Parse 0 0.00 0.00 0 0 0
> 0
> Execute 9 0.00 0.00 0 0 0
> 0
> Fetch 9 119.20 119.95 135 40086840 0
> 2111
> ------- ------ -------- ---------- ---------- ---------- ----------
> ----------
> total 18 119.20 119.96 135 40086840 0
> 2111
>
> Upon looking at the details, "OE_ORDER_LINES_ALL" seems to be the object
> which was read from disk..
>
> db file sequential read 92.7% 1,258.1501s 3,692,162 0.0003s 0.0001s
> 0.5071s
> I am now leaning towards Jonathan's suggestion of a potential large scale
> update on this table.. I will check with the team and see if there is any
> such update which happens.. With the AWR baseline created around that time,
> I am going to go through and see if I could find it..
>
> Knowing that I have all this information, is there anything else that I
> could be looking at?
>
> Thank you so much everyone
>
>
> -Upendra
>
> ------------------------------
> *From:* Dominic Brooks <dombrooks_at_hotmail.com>
> *Sent:* Friday, September 14, 2018 2:52 AM
> *To:* nupendra_at_hotmail.com
> *Cc:* Martin Berger; Oracle-L oracle-l
> *Subject:* Re: Instrumenting Poor performance
>
> Sql plan hash does not include the predicates so that’s one niche
> consideration to look out for. AWR doesn’t hold predicates so you will need
> to wait until you can pull plans from memory via dbms_xplan.display_cursor
> to see that. It’s possible but unusual.
>
> Real time sql monitoring can you tell you where the time was spent but if
> you no longer have that available for bad execution then you can get a very
> rough approximation from ASH raw data.
>
> Full sql trace is best to see what you were doing but ASH is usually good
> enough.
>
> A combination of wait events (e.g runtime decisions about switching from
> buffered to direct io) and the detail of what you are waiting on exactly
> (e.g reading lots of undo) might be sufficient to give pointers.
>
> Otherwise you might need the combination of ash/tracing (what) and
> snapping session statistics (why) to give a better picture.
>
> Regards
> Dominic
>
> Sent from my iPhone
>
> On 13 Sep 2018, at 21:47, Upendra nerilla <nupendra_at_hotmail.com> wrote:
>
> is it always the same SQL_ID?
> You an enable sql_trace for this particular SQL:
> alter system set events 'sql_trace[sql: <SQL_ID>] level=12';
>
> It is always the same sql_id. We have a 10046 and 10053 trace for the good
> execution.. Waiting for the next poor execution to capture the traces
> again..
>
>
> I assume EBS can enable tracing for specific activities, but I'm not close
> to EBS, but maybe there are better solutions than simple sql_trace.
>
> I am not an EBS guy, so I am at a loss here. :(
>
>
> Do you have proper facility to create a profile based on these sql_trace
> files?
>
> There is already a sql_profile created for the sql_id. Is that what you
> mean?
>
>
> ------------------------------
> *From:* Martin Berger <martin.a.berger_at_gmail.com>
> *Sent:* Thursday, September 13, 2018 3:52 PM
> *To:* nupendra_at_hotmail.com
> *Cc:* Oracle-L oracle-l
> *Subject:* Re: Instrumenting Poor performance
>
> Hi Upendra,
>
> is it always the same SQL_ID?
> You an enable sql_trace for this particular SQL:
> alter system set events 'sql_trace[sql: <SQL_ID>] level=12';
>
>
> I assume EBS can enable tracing for specific activities, but I'm not close
> to EBS, but maybe there are better solutions than simple sql_trace.
>
> With the traces of different "good" and "bad" and see where the time is
> spent.
>
> Do you have proper facility to create a profile based on these sql_trace
> files?
>
> br,
> berx
>
>
>
> Am Do., 13. Sep. 2018 um 21:11 Uhr schrieb Upendra nerilla <
> nupendra_at_hotmail.com>:
>
> Hello Team -
> We have an EBS application which is running EBS and several other modules
> (OTC). From time to time I see a particular query giving poor response
> time. Normal response is <4 mins and during the poor execution, it goes
> over an hour.
>
> We have a SQL baseline created for that SQL_ID and forcing the optimal
> plan. We are able to see that optimizer is using the same hash. There
> are no host resource (cpu/memory/io) constraints.. This job runs only a
> couple of times a day, very time sensitive for the business. We are unable
> to reproduce this at lower environments even when we performed refreshes..
>
> We see a pattern that this issue shows up during the first week of the
> month and disappears after a couple of days (not the same exact day).
> Here is what I am thinking of gathering - high level info..
>
> 1. Gather daily row count of all the tables involved in the query..
> 2. Review the jobs and see if there is anything unique..
>
> What else could I gather to troubleshoot this further?
> Appreciate any insights..
>
> Thank you
> -Upendra
>
>

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Niall Litchfield
Oracle DBA
http://www.orawin.info

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