Databases Reference
In-Depth Information
Clicking on the name link in the previous list we can view the corresponding report; in the
following screenshot, we can see an example of an ADDM report viewed through OEM:
There's more...
The parameter
DBIO_EXPECTED
influences the ADDM analysis of I/O performance, because
it describes the expected I/O subsystem performance, measuring the average time needed
to read a single database block. The default value of the parameter is 10 milliseconds,
corresponding to the average time of common hard disks. Please note that this measure
includes the seek time.
If our I/O subsystem is significantly slower or faster, we may end up with possible false alerts
or no alerts at all. We can adjust the parameter issuing the following statement:
EXEC DBMS_ADVISOR.SET_DEFAULT_TASK_PARAMETER('ADDM', 'DBIO_EXPECTED',
12000);
The numeric value is the time expressed in microseconds.
