RE: PGA_AGGREGATE_TARGET, AUTO PGA TARGET and WORKAREA_SIZE_POLICY

        We have tried that and more. All have had some undesirable side effect. Connection pooling got filled up and the world hanged. Dedicated is the only methodology which keeps it manageable. We have an idle process killer. Some days it's very active. Other days are not very active. It's third party stuff so we can't see what they are doing.

Elizabeth Reen

-----Original Message-----
From: Mladen Gogala [mailto:gogala.mladen_at_gmail.com] Sent: Thursday, October 12, 2017 3:30 PM To: Reen, Elizabeth [ICG-IT]; oracle-l_at_freelists.org Subject: Re: PGA_AGGREGATE_TARGET, AUTO PGA TARGET and WORKAREA_SIZE_POLICY

Hi Liz,

Have you tried DRCP ("Database Resident Connection Pooling")? Here is a page about it:

https://urldefense.proofpoint.com/v2/url?u=https-3A__docs.oracle.com_cd_B28359-5F01_server.111_b28310_manproc002.htm-23ADMIN12348&d=DwIDaQ&c=j-EkbjBYwkAB4f8ZbVn1Fw&r=yWMFosURAngbt8VLeJtKLVJGefQxustAZ9UxecV7xpc&m=Ij6AC3BhNTda8GrJSqRuifN0PfQqER-k4omj4zan89k&s=WvDtvw3ggnrq9lSGe6CHFGx74vhLYAEYPfrSUe5dlug&e=

There is also a good explanation on AskTom:

https://urldefense.proofpoint.com/v2/url?u=https-3A__asktom.oracle.com_pls_asktom_f-3Fp-3D100-3A11-3A0-3A-3A-3A-3AP11-5FQUESTION-5FID-3A22140261281764&d=DwIDaQ&c=j-EkbjBYwkAB4f8ZbVn1Fw&r=yWMFosURAngbt8VLeJtKLVJGefQxustAZ9UxecV7xpc&m=Ij6AC3BhNTda8GrJSqRuifN0PfQqER-k4omj4zan89k&s=iW94ZRdXEpdnWfZqVkRHkUld-GQ4MFvb8ZaJQIUO2rc&e=

You get the best of both worlds with DRCP.

Regards

On 10/12/2017 03:23 PM, Reen, Elizabeth wrote:
> Multithreaded is what is killing me. The app servers are creating sessions and losing track of them.
>
> Liz
>
> Elizabeth Reen
>
> -----Original Message-----
> From: oracle-l-bounce_at_freelists.org
> [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Mladen Gogala
> Sent: Wednesday, October 11, 2017 7:14 PM
> To: oracle-l_at_freelists.org
> Subject: Re: PGA_AGGREGATE_TARGET, AUTO PGA TARGET and
> WORKAREA_SIZE_POLICY
>
> Hi Liz,
>
> You don't have PGA_AGGREGATE_LIMIT on 11g. Oracle doesn't kill sessions on 11g. On 12c, a good way of avoiding PGA problems is to use multi-threaded execution mode. Oracle allocates all the memory at once, just as with the shared server configuration and manages it automatically. There are significant differences: with the shared server, the allocated memory is still shared and latches are semaphores for which you need a device driver. With multi-threading, the allocated memory is the normal process memory and latches are implemented as libpthread mutexes. If you have problems with PGA, I would use thread based implementation on Linux. The problem is with Oracle, who did not provide per-process hard limit which would prevent calloc from succeeding.
>
> Regards
>
>
> On 10/11/2017 03:35 PM, Reen, Elizabeth (Redacted sender elizabeth.reen for DMARC) wrote:
>> Sounds all too familiar, I have the same issue on AIX with the same solution. We can't find out why they are not being killed. I'm running 11 r2.
>>
>>
>> Liz
>>
>> -----Original Message-----
>> From: oracle-l-bounce_at_freelists.org
>> [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Norman Dunbar
>> Sent: Monday, October 09, 2017 4:00 PM
>> To: oracle-l_at_freelists.org
>> Subject: Re: PGA_AGGREGATE_TARGET, AUTO PGA TARGET and
>> WORKAREA_SIZE_POLICY
>>
>> On 09/10/17 20:41, Tim Gorman wrote:
>> > ....
>>> What the documentation is saying is that, when PGA_AGGREGATE_LIMIT
>>> is exceeded, the RDBMS will first "attack" sessions using lots of
>>> "untunable" PGA, because there is nothing else that the Oracle
>>> kernel can do to control that.  Tunable memory can be adjusted, but
>>> untunable memory can only be killed, and heap memory is always
>>> released with the calling operation or process is killed.
>> What I found recently, with 12c on Windows (in the cloud) was that when the PGA_AGGREGATE_LIMIT was exceeded only runnable/running sessions wre getting killed by Oracle.
>>
>> There were a number of sessions, submitted by an application server, to run reports/calculations etc. When the reports were done, the sessions should have logged out, but didn't for some as yet, unknown reason - the vendor is unable to explain why. So there were lots of sessions sitting on event "SQL*NET: message from client" for hours and hours and days and weeks (occasionally) gradually building up the amount of PGA in use.
>>
>> I saw over 650 of these idle sessions on occasions and when the PGA
>> ran out, there were "screams of horror" from the users as their
>> running sessions were killed leaving these damned idle sessions
>> untouched, and consuming PGA. The users were not happy! (And neither
>> was the DBA!)
>>
>> In the end, and in the inability of the vendor to come up with (a) a
>> reason and (b) a solution, I created a scheduled job to run every
>> half hour, until the universe ends, checking for these sessions very
>> carefully, and killing any that were previously running reports, that
>> were now idle, that were idle on the above event, had been idle for
>> over
>> 30 minutes and were executing as a particular OS User while logged in as a specific database user. That "solved" our particular problem.
>>
>> I finished that contract before the vendor had worked out what the problem was, and as far as I know from recent conversations with my now ex colleagues, they have simply said that my solution is the fix! Go figure.
>>
>> This implies, to my ageing mind, that the algorithm used by Oracle that selects the sessions to be killed is somewhat flawed perhaps? At least, on Windows.
>>
>> Just my £0.02.
>>
>>
>> Cheers,
>> Norm.
>>
>> --
>> Norman Dunbar
>> Dunbar IT Consultants Ltd
>>
>> Registered address:
>> 27a Lidget Hill
>> Pudsey
>> West Yorkshire
>> United Kingdom
>> LS28 7LG
>>
>> Company Number: 05132767
>> --
>> https://urldefense.proofpoint.com/v2/url?u=http-3A__www.freelists.org
>> _
>> webpage_oracle-2Dl&d=DwIDaQ&c=j-EkbjBYwkAB4f8ZbVn1Fw&r=yWMFosURAngbt8
>> V
>> LeJtKLVJGefQxustAZ9UxecV7xpc&m=0rZvc54Jlwk3Q8sw3qwAqIvqKrDjbf54s0JFlt
>> h L_1Y&s=nlEOhMZVzEeIZWSTJv1vJXGR4oUZPnOJK3G0V2Nw9gc&e=
>>
>>
>> i 0 zX + n { +i ^l===
> --
> Mladen Gogala
> Oracle DBA
> Tel: (347) 321-1217
>
> --
> https://urldefense.proofpoint.com/v2/url?u=http-3A__www.freelists.org_
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>
>

--
Mladen Gogala
Oracle DBA
Tel: (347) 321-1217

†Ûiÿü0ÁúÞzX¬¶Ê+ƒün– {ú+iÉ^ Received on Thu Oct 12 2017 - 21:48:03 CEST