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RE: Your opinion please...RBS

From: Kevin Kostyszyn <kevin_at_dulcian.com>
Date: Tue, 12 Dec 2000 09:29:48 -0500
Message-Id: <10708.124316@fatcity.com>


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Your opinion please...RBSWe have created large rb's (100mb) and placed them into their own rbbig tablespace, but we use them for specific tasks. Meaning, they are not online by default, however if we are going to be running a large import or export, we will turn off all of the little ones and bring these big ones online. Of course, we are a developement shop so it is probably a lot different in a production environement. kev
  -----Original Message-----
  From: root_at_fatcity.com [mailto:root_at_fatcity.com]On Behalf Of Koivu, Lisa   Sent: Tuesday, December 12, 2000 9:06 AM   To: Multiple recipients of list ORACLE-L   Subject: Your opinion please...RBS

  Good morning -

  I'm reading through some doco about rollback segments and refreshing my memory. I remember a list discussion in the past about 'what is the point of optimal' with rbs's. The book I am reading (Oracle8i DBA Handbook, Oracle Press) states that shrinking to optimal, and extending a rollback segment, are both costly.

  Seems to me if you don't have the luxury of a very large tablespace then utilizing optimal is your only way to get rbs's to share disk nicely.

  However, if extending and shrinking is that costly, and you have a ton of disk at your disposal, I wonder about making my rbs's fairly large. Optimal right now is 40M (seems large to me). Our main app is more of a hybrid system, so I see wild numbers in v$rollstat - HWM's from 40M to 300M+. Has anyone just created really large rollback segments based on these types of weird sizes?

  I also see waits in v$rollstat, and undo waits in v$waitstat. I just bumped up the number of rbs's to 26 based upon a recent HWM of 101 concurrent sessions. My waits are still growing!! Is it totally wild of me to think about adding even more rbs's?? I have more disk than I could ever realistically use in my rbs ts (10G). I am thinking about just doubling the number of rbs's because 1. I don't want to see ANY rbs waits in v$rollstat, v$waitstat and 2. because I've got the disk.

  Am I out in left field? Any comments, suggestions, swift KITA's are appreciated. Gracias

  Lisa Rutland Koivu
  *O*penly *C*ynical & *P*essimistic
  Qode.com
  4850 North State Road 7
  Suite G104
  Fort Lauderdale, FL 33319

  V: 954.484.3191, x174
  F: 954.484.2933
  C: 954.658.5849

  http://www.qode.com

  "The information contained herein does not express the opinion or position of Qode.com and cannot be attributed to or made binding upon Qode.com."

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<DIV><SPAN class=3D984422514-12122000><FONT face=3DArial color=3D#0000ff =
size=3D2>We=20
have created large rb's (100mb) and placed them into their own rbbig = tablespace,=20
but we use them for specific tasks.&nbsp; Meaning, they are not online = by=20
default, however if we are going to be running a large import or export, = we will=20
turn off all of the little ones and bring these big ones online.&nbsp; = Of=20
course, we are a developement shop so it is probably a lot different in = a=20
production environement.</FONT></SPAN></DIV> <DIV><SPAN class=3D984422514-12122000><FONT face=3DArial color=3D#0000ff =

size=3D2>kev</FONT></SPAN></DIV>
<BLOCKQUOTE dir=3Dltr style=3D"MARGIN-RIGHT: 0px">
<DIV class=3DOutlookMessageHeader dir=3Dltr align=3Dleft><FONT =
face=3DTahoma=20
  size=3D2>-----Original Message-----<BR><B>From:</B> root_at_fatcity.com=20   [mailto:root_at_fatcity.com]<B>On Behalf Of </B>Koivu, = Lisa<BR><B>Sent:</B>=20
  Tuesday, December 12, 2000 9:06 AM<BR><B>To:</B> Multiple recipients = of list=20
  ORACLE-L<BR><B>Subject:</B> Your opinion =

please...RBS<BR><BR></FONT></DIV>

<P><FONT face=3DArial size=3D2>Good morning - </FONT></P>
<P><FONT face=3DArial size=3D2>I'm reading through some doco about =
rollback=20
  segments and refreshing my memory. I remember a list discussion in the = past=20
  about 'what is the point of optimal' with rbs's.&nbsp; The book I am = reading=20
  (Oracle8i DBA Handbook, Oracle Press) states that shrinking to = optimal, and=20
  extending a rollback segment, are both costly.&nbsp; </FONT></P>
<P><FONT face=3DArial size=3D2>Seems to me if you don't have the =
luxury of a very=20
  large tablespace then utilizing optimal is your only way to get rbs's = to share=20
  disk nicely. </FONT></P>
<P><FONT face=3DArial size=3D2>However, if extending and shrinking is =
that costly,=20
  and you have a ton of disk at your disposal, I wonder about making my = rbs's=20
  fairly large.&nbsp; Optimal right now is 40M (seems large to = me).&nbsp; Our=20
  main app is more of a hybrid system, so I see wild numbers in = v$rollstat -=20
  HWM's from 40M to 300M+.&nbsp; Has anyone just created really large = rollback=20
  segments based on these types of weird sizes?</FONT></P>
<P><FONT face=3DArial size=3D2>I also see waits in v$rollstat, and =
undo waits in=20
  v$waitstat.&nbsp; I just bumped up the number of rbs's to 26 based = upon a=20
  recent HWM of 101 concurrent sessions.&nbsp; My waits are still=20   growing!!&nbsp; Is it totally wild of me to think about adding even = more=20
  rbs's??&nbsp; I have more disk than I could ever realistically use in = my rbs=20
  ts (10G). I am thinking about just doubling the number of rbs's = because 1. I=20
  don't want to see ANY rbs waits in v$rollstat, v$waitstat and 2. = because I've=20
  got the disk. </FONT></P>
<P><FONT face=3DArial size=3D2>Am I out in left field?&nbsp; Any =
comments,=20
  suggestions, swift KITA's are appreciated.&nbsp; Gracias</FONT> </P>
<P><B><FONT face=3DArial size=3D1>Lisa Rutland Koivu</FONT></B> =
<BR><FONT=20
  face=3DArial size=3D1>*O*penly *C*ynical &amp;&nbsp; = *P*essimistic</FONT>=20
<BR><FONT face=3DArial size=3D1>Qode.com</FONT> <BR><FONT face=3DArial =
size=3D1>4850=20
  North State Road 7</FONT> <BR><FONT face=3DArial size=3D1>Suite = G104</FONT>=20
<BR><FONT face=3DArial size=3D1>Fort Lauderdale, FL&nbsp; 33319</FONT> =
</P>
<P><FONT face=3DArial size=3D1>V: 954.484.3191, x174</FONT> <BR><FONT =
face=3DArial=20
  size=3D1>F: 954.484.2933 </FONT><BR><FONT face=3DArial size=3D1>C:=20   954.658.5849</FONT> <BR><FONT face=3DArial size=3D1><A target=3D_blank =

  href=3D"http://www.qode.com">http://www.qode.com</A></FONT> </P>
<P><I><FONT face=3DArial color=3D#000000 size=3D1>"The information =
contained herein=20
  does not express the opinion or position of Qode.com and cannot be = Received on Tue Dec 12 2000 - 08:29:48 CST

Original text of this message

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