Which three statements correctly describe the features of the I/O calibration process?
(Choose three.)
A.
Only one I/O calibration process can run at a time.
B.
It automates the resource allocation for the Automated Maintenance Tasks.
C.
It improves the performance of the performance-critical sessions while running.
D.
It can be used to estimate the maximum number of I/Os and maximum latency time for
the system.
E.
The latency time is computed only when the TIMED_STATISTICS initialization parameter
is set to TRUE.
http://docs.oracle.com/cd/E11882_01/server.112/e41573/iodesign.htm#PFGRF94383
8.3.1 Prerequisites for I/O Calibration
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 toSETALL.
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.
A, D, E are correct:
https://docs.oracle.com/cd/B28359_01/server.111/b28274/iodesign.htm
A: Additionally, only one calibration can be performed on a database instance at a time.
D: 8.2.2 Running I/O Calibration
The I/O calibration feature of Oracle Database is accessed using the DBMS_RESOURCE_MANAGER.CALIBRATE_IO procedure. This procedure issues an I/O intensive read-only workload (made up of one megabytes of random of I/Os) to the database files to determine the maximum IOPS (I/O requests per second) and MBPS (megabytes of I/O per second) that can be sustained by the storage subsystem. Due to the overhead from running the I/O workload, I/O calibration should only be performed when the database is idle, or during off-peak hours, to minimize the impact of the I/O workload on the normal database workload.
E: timed_statistics must be set to TRUE