Oracle-L: Re: Direct SGA Access

From: Anjo Kolk <anjo_at_oraperf.com>
Date: Fri, 11 Apr 2003 10:48:24 -0800
Message-ID: <F001.0057FC12.20030411104824@fatcity.com>

Direct SGA AccessYou probably don't have to pay for it ;-)

There are several products out there that attach to the SGA directly without any problems. Some products you probably don't even know that they do and you probably don't care.

I can see a couple reasons for attaching to the SGA:

low overhead sampling, non-intrusive
combining, in a few lines of code, data that oracle can only do with several joins over multiple tables.
in case of a hang you can still see what is going on (or not going on).

Anjo

Original Message ----- From: Gogala, Mladen To: Multiple recipients of list ORACLE-L Sent: Friday, April 11, 2003 6:19 PM Subject: RE: Direct SGA Access

The other solution would be to redefine a second. I am still inclined to consider a bigger box before trying to shmat an SGA of a database. -----Original Message-----
From: Cary Millsap [mailto:cary.millsap_at_hotsos.com] Sent: Friday, April 11, 2003 11:54 AM To: Multiple recipients of list ORACLE-L Subject: RE: Direct SGA Access

Dick,

To answer your question about motive, the reason someone might want to is that unless you can poll the V$ structures 100 times per second, you miss important event occurrences. It's impossible to do this with SQL. Not difficult. Impossible.

One test that'll be documented in my book in a few months is a query upon a 50-row V$SESSION fixed view. Our 800MHz Linux server can only do about 65 queries/second. And that's just one of about 30 fixed views that would need to be queried. And that's just with 50 sessions going (not the hundreds that most people have).

    Cary Millsap
    Hotsos Enterprises, Ltd.
    http://www.hotsos.com

Upcoming events:

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Visit www.hotsos.com for schedule details...
IOUG-A Live 2003, Orlando, 10am Monday 28 April: Oracle Operational Timing Data

-----Original Message-----
From: root_at_fatcity.com [mailto:root_at_fatcity.com] On Behalf Of Goulet, Dick Sent: Thursday, April 10, 2003 4:59 PM To: Multiple recipients of list ORACLE-L Subject: RE: Direct SGA Access

Raj,

Why are you trying to access the SGA? There are plenty of dynamic performance views to extract data from & messing with the SGA may cause your DB to crash.

    Dick Goulet
    Senior Oracle DBA
    Oracle Certified 8i DBA

-----Original Message-----
From: Jamadagni, Rajendra [mailto:Rajendra.Jamadagni_at_espn.com] Sent: Thursday, April 10, 2003 5:39 PM To: Multiple recipients of list ORACLE-L Subject: Direct SGA Access

Has anyone been able to make direct SGA access work for 64 bit databases? My C knowledge is as good as my lisp knowledge, i.e. just about zero.

I tried playing with the xksuse.c, but all it does is dumps core ...

If anyone has done this successfully, could you please let me know what needs to be changed in the code?

Thanks in advance
Raj

Rajendra dot Jamadagni at nospamespn dot com All Views expressed in this email are strictly personal. QOTD: Any clod can have facts, having an opinion is an art !

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Author: Anjo Kolk
  INET: anjo_at_oraperf.com

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Received on Fri Apr 11 2003 - 13:48:24 CDT