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.
The I/O calibration feature of Oracle Database enables you to assess the performance of the storage subsystem, and determine whether I/O performance problems are caused by the database or the storage subsystem.
Prerequisites for I/O Calibration
• The user must be granted the SYSDBA privilege
• timed_statistics must be set to TRUE
• Asynchronous I/O must be enabled
• Ensure that asynchronous I/O is enabled for data files by running the following query
• Only one calibration can be performed on a database instance at a time.
The output parameter actual_latency provides the average latency for this workload. When you need a specific target latency, you can specify the target latency with the input parameter max_latency (specifies the maximum tolerable latency in milliseconds for database-block-sized IO requests).
The second step of calibration using the DBMS_RESOURCE_MANAGER.CALIBRATE_IO procedure issues random, 1 MB reads to all data files from all database instances. The second step yields the output parameter max_mbps, which specifies the maximum MBPS of I/O that the database can sustain. This step provides an important metric for data warehouses.