RE: CPU Problem

> We are facing with some CPU problem (cpu 100% usage!),

To offer another point of view:

There are some queries, especially in a data warehouse, that are large queries, that must, by the nature of the information sought, sort through large amounts of data. The RDBMS, in an attempt to satisfy the query as quickly as possible, is going to use its CPU resources to their full extent. ANY time an Oracle query is being run, be it big or small, elegant or trashy, it will use all the CPU that the OS will allow it to use; and the OS will run a CPU to 100% of its capacity when there is work to be done. Most of the time, things come and go fast enough on a system that you don't see those momentary 100% spikes in CPU usage. Think about it: Why would the OS deliberately drag its feet in getting work done? Is this some kind of union-made OS?

This is a explanation that I have given many times to sys admins that expressed alarm that an Oracle process was using 100% of a CPU. It SHOULD to do that!

Now, if this is a database in which one should not be seeing large, long-running queries, to quote Emily Littella: "Well, that's different!" The decision as to whether you have a problem should not be based on some percentage of CPU usage, but on what is "normal" usage for this particular database.

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Author: Stephen Lee
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