Re: new paper on direct access in C to the SGA
- From: Mogens Nørgaard <mln@xxxxxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Wed, 16 Jun 2004 09:57:20 +0200
It's actually very surprising for a database fan to see how much work
can be done on a compute with very little resource usage if you don't go
through the database engine :-). Two reasons for DMA techniques: To
sample fast enough, to reduce overhead of the sampling, and to access
information not available (externalized) yet from the vendor.
Those are the reasons Precise/Veritas (and others I don't know about) do
DMA. It's in some ways back to the roots :). Dangerous? I agree with
Mladens points on this - the answer is basically no.
Mogens
Goulet, Dick wrote:
Mladen,
Most applications that I've heard on that want to do this want to be installed by the database owner, therefore permissions are no longer a preventative. On top of all that, the SGA's contents are trade secrets of Oracle. I'm sure they are not talking about it, so those who "know" what their talking about have surmised it from experimentation. I know of enough experimenters running around sans limbs to stay away from that. And anyway, going through the database engine for something like this does not place such a high load on the system that it really matters. Not to mention that this program has to run on the local machine which then has it competing for the attention of the same CPU(s) and memory as the database. And theirs nothing I can think of that slows a system down more than having the swapper working.
Dick Goulet
Senior Oracle DBA
Oracle Certified 8i DBA
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