RE: DATABASE SLOW(8170 ON SUN SOLARIS)

From: Niall Litchfield <n-litchfield_at_audit-commission.gov.uk>
Date: Tue, 04 May 2004 10:03:47 +0100
Message-Id: <s0976a9d.089@bristol21.bristol.ac>

Hi Abhishek

I have a question and a comment

> The cost
> calculated by the CBO is primarily comprised of physical I/O.
> =3D The actual formula is documented as=3D20 IO + CPU/1000 +
> NetIO*1.5 In this formula, "IO" represents physical I/O
> requests, "CPU" represents =3D logical I/O requests, and "Net
> I/O" represents logical I/O requests =3D to/from a remote
> database across a database link.

Any pointer to where this comes from would be good. I assume this is intend= ed to be the formula for the cost of index block access?

> This implies that physical
> I/O requests are the most expensive =3D component, so they make
> up the majority of the costing.

It implies that physical IO is costed at 1000 times the cost of logical IO,=
 which would probably be a poor estimate, and somewhat surprisingly suggest=
s that network IO is only 50% more expensive than reading from a local disk=

.=20

Cheers

Niall Litchfield
Oracle DBA
Audit Commission
+44 117 975 7805=20

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Received on Tue May 04 2004 - 04:01:32 CDT