Before running I/O calibration, ensure that the following requirements are met:
The user must be granted the SYSDBA privilege
timed_statistics must be set to TRUE
Asynchronous I/O must be enabled
When using file systems, asynchronous I/O can be enabled by setting the FILESYSTEMIO_OPTIONS initialization parameter to SETALL.
Ensure that asynchronous I/O is enabled for data files by running the following query:
COL NAME FORMAT A50 SELECT NAME,ASYNCH_IO FROM V$DATAFILE F,V$IOSTAT_FILE I WHERE F.FILE#=I.FILE_NO AND FILETYPE_NAME='Data File';
Additionally, only one calibration can be performed on a database instance at a time.
When running the DBMS_RESOURCE_MANAGER.CALIBRATE_IO procedure, consider the following:
Only run one calibration at a time on databases that use the same storage subsystem. If you simultaneously run the calibration across separate databases that use the same storage subsystem, the calibration will fail.
Quiesce the database to minimize I/O on the instance.
For Oracle Real Application Clusters (Oracle RAC) configurations, ensure that all instances are opened to calibrate the storage subsystem across nodes.
For an Oracle Real Application Clusters (Oracle RAC) database, the workload is simultaneously generated from all instances.
The num_physical_disks input parameter is optional. By setting the num_physical_disks parameter to the approximate number of physical disks in the database's storage system, the calibration can be faster and more accurate.
In some cases, asynchronous I/O is permitted for data files, but the I/O subsystem for submitting asynchronous I/O may be maximized, and I/O calibration cannot continue. In such cases, refer to the port-specific documentation for information about checking the maximum limit for asynchronous I/O on the system.
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