Re: Buffer cache hits %

From: Xuening Sun <ba503_at_torfree.net>
Date: Fri, 16 Jul 1999 13:09:03 GMT
Message-ID: <FEysJ4.GI7.0.bloor@torfree.net>

Kevin,

Basically, if the buffer cache hits ratio is over 90%, it is good or acceptable in most cases. But you need to look at other issues at OS level, like if allocating a big chunck of physical memory for buffer cache causes heavy swapping for the HP server, you might want to reduce the size of buffer cache (the hit ratio might go down as well)

Xuening Sun
--
Kevin Gillins (kevin_gillins_at_compuserve.com) wrote:
: This is a multi-part message in MIME format.

: ------=_NextPart_000_0015_01BECE98.2C81AF80
: Content-Type: text/plain;
: charset="iso-8859-1"
: Content-Transfer-Encoding: 7bit

: I have a question about the buffer cache hits ratio we are experiencing.

: We are on 7.3.3.5 database using 10.7 oracle apps most all products. Apx
: 100+ users.
: The database size is apx 40 gig. We are on HP 4 processors with 2.5 gig
: memory.
: There are 2 instances both the same size (prod and test). The shared pool
: is set
: at 250,000,000 running 6 db writers. The production instance is on EMC
: disks.

: My main question is the buffer cache hit% is sitting at 90% in general. Is
: this good, bad or
: real bad. I want to get a feel. I have tried increasing the shared pool
: and db_block_buffers.

: What other settings if any would improve this statistic. What stats could I
: check to see
: what contributes to the 10% miss?

: Your suggestions and answers are appreciated.

: --

: Kevin Gillins
: Management Information Consulting
: Boston Office
: 978-887-3300

: ------=_NextPart_000_0015_01BECE98.2C81AF80
: Content-Type: text/html;
: charset="iso-8859-1"
: Content-Transfer-Encoding: quoted-printable

: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
: <HTML><HEAD>
: <META content=3D"text/html; charset=3Diso-8859-1" =
: http-equiv=3DContent-Type>
: <META content=3D"MSHTML 5.00.2314.1000" name=3DGENERATOR>
: <STYLE></STYLE>
: </HEAD>
: <BODY bgColor=3D#ffffff>
: <DIV><FONT size=3D2>I have a question about the buffer cache hits ratio =
: we are=20
: experiencing.</FONT></DIV>
: <DIV> </DIV>
: <DIV><FONT size=3D2>We are on 7.3.3.5 database using 10.7 oracle apps =
: most all=20
: products.  Apx 100+ users.</FONT></DIV>
: <DIV><FONT size=3D2>The database size is apx 40 gig.  We are on =
: HP 4=20
: processors with 2.5 gig memory.</FONT></DIV>
: <DIV><FONT size=3D2>There are 2 instances both the same size (prod and=20
: test).  The shared pool is set</FONT></DIV>
: <DIV><FONT size=3D2>at 250,000,000 running 6 db writers.  The =
: production=20
: instance is on EMC disks.</FONT></DIV>
: <DIV> </DIV>
: <DIV><FONT size=3D2>My main question is the buffer cache hit% is sitting =
: at 90% in=20
: general.  Is this good, bad or</FONT></DIV>
: <DIV><FONT size=3D2>real bad.  I want to get a feel.  I have =
: tried=20
: increasing the shared pool and db_block_buffers.</FONT></DIV>
: <DIV> </DIV>
: <DIV><FONT size=3D2>What other settings if any would improve this =
: statistic. =20
: What stats could I check to see </FONT></DIV>
: <DIV><FONT size=3D2>what contributes to the 10% miss?</FONT></DIV>
: <DIV> </DIV>
: <DIV><FONT size=3D2>Your suggestions and answers are =
: appreciated.</FONT></DIV>
: <DIV><FONT size=3D2><BR>-- <BR><BR>Kevin Gillins<BR>Management =
: Information=20
: Consulting<BR>Boston Office<BR>978-887-3300</FONT></DIV>
: <DIV> </DIV>
: <DIV><FONT size=3D2></FONT> </DIV></BODY></HTML>

: ------=_NextPart_000_0015_01BECE98.2C81AF80--

-- Received on Fri Jul 16 1999 - 08:09:03 CDT