DBMS_RESOURCE_MANAGER.CALIBRATE_IO

Introduced in Oracle Database 11g Release 1, the CALIBRATE_IO procedure gives an idea of the capabilities of the storage system from within Oracle. There are a few restrictions associated with the procedure.

• The procedure must be called by a user with the SYSDBA priviledge.
• TIMED_STATISTICS must be set to TRUE, which is the default when STATISTICS_LEVEL is set to TYPICAL.
• Datafiles must be accessed using asynchronous I/O. This is the default when ASM is used.

You can check your current asynchronous I/O setting for your datafiles using the following query.

SELECT d.name,
       i.asynch_io
FROM   v$datafile d,
       v$iostat_file i
WHERE  d.file# = i.file_no
AND    i.filetype_name  = 'Data File';

NAME                                               ASYNCH_IO
-------------------------------------------------- ---------
/u01/app/oracle/oradata/DB11G/system01.dbf         ASYNC_OFF
/u01/app/oracle/oradata/DB11G/sysaux01.dbf         ASYNC_OFF
/u01/app/oracle/oradata/DB11G/undotbs01.dbf        ASYNC_OFF
/u01/app/oracle/oradata/DB11G/users01.dbf          ASYNC_OFF
/u01/app/oracle/oradata/DB11G/example01.dbf        ASYNC_OFF

5 rows selected.

SQL>

To turn on asynchronous I/O, issue the following command and restart the database.

ALTER SYSTEM SET filesystemio_options=setall SCOPE=SPFILE;

Provided your storage supports asynchronous I/O, the ASYNC_IO flag should now have changed.

SELECT d.name,
       i.asynch_io
FROM   v$datafile d,
       v$iostat_file i
WHERE  d.file# = i.file_no
AND    i.filetype_name  = 'Data File';

NAME                                               ASYNCH_IO
-------------------------------------------------- ---------
/u01/app/oracle/oradata/DB11G/system01.dbf         ASYNC_ON
/u01/app/oracle/oradata/DB11G/sysaux01.dbf         ASYNC_ON
/u01/app/oracle/oradata/DB11G/undotbs01.dbf        ASYNC_ON
/u01/app/oracle/oradata/DB11G/users01.dbf          ASYNC_ON
/u01/app/oracle/oradata/DB11G/example01.dbf        ASYNC_ON

5 rows selected.

SQL>

You can now call the procedure by running the following code.

CONN / AS SYSDBA

SET SERVEROUTPUT ON
DECLARE
  l_latency  PLS_INTEGER;
  l_iops     PLS_INTEGER;
  l_mbps     PLS_INTEGER;
BEGIN
   DBMS_RESOURCE_MANAGER.calibrate_io (num_physical_disks => 1, 
                                       max_latency        => 20,
                                       max_iops           => l_iops,
                                       max_mbps           => l_mbps,
                                       actual_latency     => l_latency);

  DBMS_OUTPUT.put_line('Max IOPS = ' || l_iops);
  DBMS_OUTPUT.put_line('Max MBPS = ' || l_mbps);
  DBMS_OUTPUT.put_line('Latency  = ' || l_latency);
END;
/

Max IOPS = 95
Max MBPS = 449
Latency  = 20

PL/SQL procedure successfully completed.

SQL>

In addition to appearing on screen, the results of a calibration run can be displayed using the DBA_RSRC_IO_CALIBRATE view.

SET LINESIZE 100
COLUMN start_time FORMAT A20
COLUMN end_time FORMAT A20

SELECT TO_CHAR(start_time, 'DD-MON-YYY HH24:MI:SS') AS start_time,
       TO_CHAR(end_time, 'DD-MON-YYY HH24:MI:SS') AS end_time,
       max_iops,
       max_mbps,
       max_pmbps,
       latency,
       num_physical_disks AS disks
FROM   dba_rsrc_io_calibrate;

START_TIME           END_TIME               MAX_IOPS   MAX_MBPS  MAX_PMBPS    LATENCY      DISKS
-------------------- -------------------- ---------- ---------- ---------- ---------- ----------
20-JUL-010 18:07:21  20-JUL-010 18:13:55          95        449        461         20          1

SQL>

https://oracle-base.com/articles/misc/measuring-storage-performance-for-oracle-systems