As with any major application environment on a machine, Oracle sometimes seems to get a bad press due to claims that it is 'resource hungry'. An error within Oracle means that it is not helping itself to dispel these rumors.

The V$ Tables within Oracle provide a wealth of useful performance information. The most common starting point for people looking at performance statistics is CPU usage. One sees the CPU used by an Oracle instance by looking at 'V$SYSSTAT: CPU used by this session'.

Dependent on other factors, this can show alarming results. In certain circumstances, the amount of CPU time recorded will be aggregated interval by interval, if you are collecting this data over a number of periods of time. Eventually this can mean that the total number of seconds CPU consumed by Oracle in an interval is greater than the number of processing seconds actually available, clearly nonsensical. Plot Oracle CPU time on a graph using a product such as
Metron's Athene software. If you see the Oracle CPU figure going up, up, up, the you know you have the problem. Oracle is not using more and more CPU necessarily, but it is probably reporting wrongly what it does use.

It is a known Oracle problem and is related to the interaction with JOB_QUEUE_PROCESSES. The resolution and full explanation is available from Oracle, bug reference 1286684, and can be downloaded from the Oracle web site.