Question: I noticed the
dbms_resource_manager.calibrate_io procedure and I was
wondering how dbms_resource_manager.calibrate_io can be used
to monitor Oracle disk I/O. Also, what does the
calibrate I/O procedure do?
dbms_resource_manager.calibrate_io stored procedure is used
to generate a randomized read-only workload for volumetric
The calibration of the I/O is used
to determine the amount of megabytes per second of data
volume that can used on the database without performance
degradation. There are a few restrictions
associated with the procedure.
- The TIMED_STATISTICS
parameter must be set to TRUE, which is the default when
- Data files must be accessed
using asynchronous I/O. This is the default when ASM is
- The procedure must be called by a user with the
You can check your current
asynchronous I/O setting for your data files using this
d.file# = i.file_no
= 'Data File';
dbms_resource_manager.calibrate_io is not to be used in a
production environment. Rather, it is to be used in a
test database to generate specific workload volumes.
Here is a sample invocation of
1 /* # of disks */
, 10 /*
maximum tolerable latency in milliseconds */
, iops /* I/O rate per second */
, mbps /* throughput, MB per second */
, lat /* actual latency in milliseconds */
DBMS_OUTPUT.PUT_LINE('max_iops = ' || iops);
DBMS_OUTPUT.PUT_LINE('latency = ' || lat);
DBMS_OUTPUT.PUT_LINE('max_mbps = ' || mbps);
The procedure calibrate_io of the package
dbms_resource_manager accepts two INOUT parameters:
- num_physical_disks - This is the number of physical disks
- max_latency - This is the
maximum latency for the disk access (in milliseconds)
And it has three OUT parameters.
After running this
procedure you can view the results using the
v$io_calibration_status and for RAC, the
- max_iops - This is the max number of I/O operations/ per
- max_mbps - This is the maximum
Megabytes per second.
- actual_latency - This is the actual latency observed during the test.
The results from this output will be displayed in these
- v$io_calibration_status: This will
show you the progress of the I/O calibration task:
* from v$io_calibration_status
view: This will show all three of the output
parameters. Plus the two input parameters, and a start_time
and end_time for multiple calibration runs:
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