View the exhibit and examine the output.
Which statement can be an inference from the output?
A.
The FRA disk group has an asynchronous I/O bottleneck
B.
The least number of I/Os are performed on the last data file in the list
C.
The number of times that the backup or restore process directed the OS to wait until an I/O was
complete is the highest for the last data file in the list
D.
The number of times that the backup or restore process made an OS call to poll for I/O
completion in Nonblocking mode is the least for the FRA disk group
Explanation:
NO EXHIBIT – ANSWER impossible / A) is set as placeholder
Oracle Press 1Z0-053 Exam Guide, Chapter 8: Monitoring and Tuning RMAN
Monitoring Asynchronous I/O
To monitor asynchronous I/O operations, you use the dynamic performance view
V$BACKUP_ASYNC_IO. The key columns to watch are the following:
– IO_COUNT: Number of I/Os performed on the file
– LONG_WAITS: Number of times the backup or restore process had to tell the OS to wait for the
I/O to complete
– SHORT_WAIT_TIME_TOTAL: Total time, in hundredths of a second, taken for
nonblockingpolling for I/O completion
The largest ratio of LONG_WAITS to IO_COUNT is a likely bottleneck in the backup process.
SHORT_WAIT_TIME_TOTAL and LONG_WAIT_TIME_TOTAL are also indicators of a bottleneck
if they are nonzero.For these two files, you may consider increasing the multiplexing to decrease or eliminate the wait
times when backing them up.
Exam Tip:
If you are using synchronous I/O but you have set BACKUP_DISK_IO_SLAVES to TRUE, then
the I/O performance is monitored in V$BACKUP_ASYNC_IO.
