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Home -> Community -> Mailing Lists -> Oracle-L -> Re: Latch 'parallel query qref latch'
Ben:
As I said in my previous post, you may get a lot of waits on this latch and that is not necessarily something to be overly concerned about. However, you can lower this number by increasing the PARALLEL_MAX_SERVERS parameter. This is the maximum number of servers that are allowed to exist concurrently. Set the value to:
(max # of concurrent PQO users) * (their max degree of parallelism) * 2
HTH!
-- Jon Walthour, OCDBA Oracle DBA Computer Horizons Cincinnati, Ohio > From: "Ben Jones" <benjonesz123_at_hotmail.com> > Organization: Fat City Network Services, San Diego, California > Reply-To: ORACLE-L_at_fatcity.com > Date: Fri, 15 Jun 2001 00:05:48 -0800 > To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> > Subject: RE: Latch 'parallel query qref latch' > > > Jon, > > Thanks for the email. My next question is fairly obvious...I'm getting a > "lot" of waits on this latch (up to 5% of all waits) - how do I tune it ? > (We've got a pretty typical environment here, a few big tables with parallel > degree 4, on a 2 cpu box with 2G of RAM, and only a couple of end users > doing big queries)... > > Any guidelines (from anybody) would be much appreciated... > > TIA > Ben >Received on Fri Jun 15 2001 - 06:20:54 CDT
>> From: "Jon Walthour" <jwalthour_at_mac.com>
>> Reply-To: ORACLE-L_at_fatcity.com
>> To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
>> Subject: RE: Latch 'parallel query qref latch'
>> Date: Thu, 14 Jun 2001 13:01:56 -0800
>>
>>
>>
>> Ben:
>>
>> The qref latch is obtained for each Parallel Query process. It
>> is acquired before the queue buffers can be manipulated so that
>> communication can take place between the various slave processes.
>> The latch is acquired for putting messages into the buffer. You
>> will generally see lots of misses for this latch since it is
>> acquired with a nowait option.
>>
>> Jon Walthour, OCDBA
>> Oracle DBA
>> Computer Horizons
>> Cincinnati, Ohio
>>
>>> --- Original Message --- >>> From: "Ben Jones" <benjonesz123_at_hotmail.com> >>> To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> >>> Date: 6/14/01 1:56:36 PM >>>
>>
>>> Does anyone know what causes waits on this latch ? >>> >>> Thanks >>> Ben >>> _________________________________________________________________________ >>> Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. >>> >>> -- >>> Please see the official ORACLE-L FAQ: http://www.orafaq.com >>> -- >>> Author: Ben Jones >>> INET: benjonesz123_at_hotmail.com >>> >>> Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 >>> San Diego, California -- Public Internet access / Mailing
>> Lists
>>> -------------------------------------------------------------------- >>> To REMOVE yourself from this mailing list, send an E-Mail message >>> to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru')
>> and in
>>> the message BODY, include a line containing: UNSUB ORACLE-L >>> (or the name of mailing list you want to be removed from).
>> You may
>>> also send the HELP command for other information (like subscribing). >>>
>>
>>
>> --
>> Please see the official ORACLE-L FAQ: http://www.orafaq.com
>> --
>> Author: Jon Walthour
>> INET: jwalthour_at_mac.com
>>
>> Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
>> San Diego, California -- Public Internet access / Mailing Lists
>> --------------------------------------------------------------------
>> To REMOVE yourself from this mailing list, send an E-Mail message
>> to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
>> the message BODY, include a line containing: UNSUB ORACLE-L
>> (or the name of mailing list you want to be removed from). You may
>> also send the HELP command for other information (like subscribing).
> > _________________________________________________________________________ > Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. > > -- > Please see the official ORACLE-L FAQ: http://www.orafaq.com > -- > Author: Ben Jones > INET: benjonesz123_at_hotmail.com > > Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 > San Diego, California -- Public Internet access / Mailing Lists > -------------------------------------------------------------------- > To REMOVE yourself from this mailing list, send an E-Mail message > to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in > the message BODY, include a line containing: UNSUB ORACLE-L > (or the name of mailing list you want to be removed from). You may > also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Jon Walthour INET: jwalthour_at_mac.com Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
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