RE: Suggestions Needed: Latch free

From: Bobak, Mark <Mark.Bobak_at_il.proquest.com>
Date: Wed, 07 Jan 2004 16:29:26 -0800
Message-ID: <F001.005DC068.20040107162926@fatcity.com>

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It usually involves rewriting the application. Ideally, (in the perfect world), each required SQL is hard parsed once (by whomever is the first to execute it since the last bounce), that person should never need to parse it again, just rebind and re-execute as needed. Users connecting later will parse once (this will be a soft parse cause it's in the cache from the first guy parsing it), and then rebind and re-execute as needed. Often, with application designs the way they are, and particularly with pre-packaged apps, this is difficult.
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-Mark
=20
=20
=20
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Mark J. Bobak=20
Oracle DBA=20
ProQuest Company=20
Ann Arbor, MI=20
"Imagination was given to man to compensate him for what he is not, and a sense of humor was provided to console him for what he is." --Unknown

	-----Original Message-----
	From: Ryan [mailto:ryan.gaffuri_at_cox.net]=20
	Sent: Wednesday, January 07, 2004 7:15 PM
	To: Multiple recipients of list ORACLE-L
	Subject: Re: Suggestions Needed: Latch free - library cache

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how do you limit excessive soft parsing?=20

Original Message -----=20 From: Bobak, Mark <mailto:Mark.Bobak_at_il.proquest.com> =20 To: Multiple recipients of list ORACLE-L <mailto:ORACLE-L_at_fatcity.com> =20 Sent: Wednesday, January 07, 2004 5:59 PM Subject: RE: Suggestions Needed: Latch free - library cache

		Tracy,
		=20
		What Oracle version?  If you're not patched up to the

latest patchset for your release, it's always a good idea to do so, as library cache bugs seem to invariably appear in every release.

		=20
		Has your code changed recently?  Has your usage
increased recently?
		=20
		Finally, library cache latch contention can be a sign of

excessive soft parsing (hard parsing usually causes more shared pool latch contention). Do you have session_cached_cursors set?

		=20
		Just some thoughts....
		=20
		-Mark
		=20
		=20

		Mark J. Bobak=20
		Oracle DBA=20
		ProQuest Company=20
		Ann Arbor, MI=20
		"Imagination was given to man to compensate him for what

he is not, and a sense of humor was provided to console him for what he is." --Unknown

			-----Original Message-----
			From: Tracy Rahmlow
[mailto:tracy.rahmlow_at_aexp.com]=20
			Sent: Wednesday, January 07, 2004 5:40 PM
			To: Multiple recipients of list ORACLE-L
			Subject: Suggestions Needed: Latch free -
library cache
		=09
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			We have experienced intermittent problems (slow

response time) with our oltp database today. There appears to be a large number of latch free events and the p2 parameter is indicating an issue with the library cache. Any thoughts on where to go next?=20

			American Express made the following
			annotations on 01/07/2004 03:36:25 PM

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<DIV><SPAN class=3D551522500-08012004><FONT face=3DArial color=3D#0000ff =

size=3D2>It=20
usually involves rewriting the application.  Ideally, (in the = perfect=20
world), each required SQL is hard parsed once (by whomever is the first = to=20
execute it since the last bounce), that person should never need to = parse it=20
again, just rebind and re-execute as needed.  Users connecting = later will=20
parse once (this will be a soft parse cause it's in the cache from the = first guy=20
parsing it), and then rebind and re-execute as needed.  Often, with =

application designs the way they are, and particularly with pre-packaged = apps,=20
this is difficult.</FONT></SPAN></DIV>
<DIV><SPAN class=3D551522500-08012004><FONT face=3DArial color=3D#0000ff =

size=3D2></FONT></SPAN> </DIV>
<DIV><SPAN class=3D551522500-08012004><FONT face=3DArial color=3D#0000ff =

size=3D2>-Mark</FONT></SPAN></DIV>
<DIV><SPAN class=3D551522500-08012004><FONT face=3DArial color=3D#0000ff =

size=3D2></FONT></SPAN> </DIV>
<DIV><SPAN class=3D551522500-08012004><FONT face=3DArial color=3D#0000ff =

size=3D2></FONT></SPAN> </DIV>

<DIV><FONT face=3DArial color=3D#0000ff size=3D2></FONT>&nbsp;</DIV>
<DIV>&nbsp;</DIV><!-- Converted from text/rtf format -->
<P><SPAN lang=3Den-us><FONT face=3D"Comic Sans MS" color=3D#008000 =

size=3D2>Mark J.=20
Bobak</FONT></SPAN> <BR><SPAN lang=3Den-us><FONT face=3D"Comic Sans MS"=20 color=3D#008000 size=3D2>Oracle DBA</FONT></SPAN> <BR><SPAN = lang=3Den-us><FONT=20
face=3D"Comic Sans MS" color=3D#008000 size=3D2>ProQuest = Company</FONT></SPAN>=20
<BR><SPAN lang=3Den-us><FONT face=3D"Comic Sans MS" color=3D#008000 =

size=3D2>Ann Arbor,=20
MI</FONT></SPAN> <BR><SPAN lang=3Den-us><B><FONT face=3DArial =
size=3D2>"Imagination=20

was given to man to compensate him for what he is not, and a sense of = humor was=20
provided to console him for what he is."  = --Unknown</FONT></B></SPAN></P>
<BLOCKQUOTE dir=3Dltr style=3D"MARGIN-RIGHT: 0px">   <DIV></DIV>
  <DIV class=3DOutlookMessageHeader lang=3Den-us dir=3Dltr = align=3Dleft><FONT=20
  face=3DTahoma size=3D2>-----Original Message-----<BR><B>From:</B> Ryan =

  [mailto:ryan.gaffuri_at_cox.net] <BR><B>Sent:</B> Wednesday, January 07, = 2004=20
  7:15 PM<BR><B>To:</B> Multiple recipients of list = ORACLE-L<BR><B>Subject:</B>=20
  Re: Suggestions Needed: Latch free - library = cache<BR><BR></FONT></DIV>
  <DIV><FONT face=3DArial size=3D2>how do you limit excessive soft = parsing?=20
  </FONT></DIV>
  <BLOCKQUOTE dir=3Dltr=20

  style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
    <DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>

<DIV=20
style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: = black"><B>From:</B>=20

<A title=3DMark.Bobak_at_il.proquest.com=20 href=3D"mailto:Mark.Bobak_at_il.proquest.com">Bobak, Mark</A> </DIV> <DIV style=3D"FONT: 10pt arial"><B>To:</B> <A = title=3DORACLE-L_at_fatcity.com=20

href=3D"mailto:ORACLE-L_at_fatcity.com">Multiple recipients of list = ORACLE-L</A>=20

</DIV>
<DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Wednesday, January 07, = 2004 5:59=20

PM</DIV>
<DIV style=3D"FONT: 10pt arial"><B>Subject:</B> RE: Suggestions = Needed: Latch=20

    free - library cache</DIV>
    <DIV><BR></DIV>
    <DIV><SPAN class=3D394255522-07012004><FONT face=3DArial = color=3D#0000ff=20

size=3D2>Tracy,</FONT></SPAN></DIV>
<DIV><SPAN class=3D394255522-07012004><FONT face=3DArial = color=3D#0000ff=20