While backing up to the Oracle Fast Recovery Area (FRA), you determined the backup is taking too long and suspect a performance bottleneck. Which three are true about diagnosing and tuning these problems? (Choose three.) 

Answer options:

A. If an RMAN BACKUP VALIDATE command takes roughly the same time as an actual backup, then both read and write I/O are likely bottlenecks.
B. Setting DBWR_IO_SLAVES to a non zero value can improve backup performance when using synchronous I/O.
C. If an RMAN BACKUP VALIDATE command takes noticeably less than an actual backup, then write I/O is a likely bottleneck.
D. If an RMAN BACKUP VALIDATE command takes roughly the same time as an actual backup, then read I/O is a likely bottleneck.
E. Data files with a high value in V$BACKUP_SYNC_IO.DISCRETE_BYTES_PER_SECOND are a potential performance bottleneck when synchronous I/O is used.
F. Setting DBWR_IO_SLAVES to a non zero value can improve backup performance when using asynchronous I/O/
G. Data files with a high value in V$BACKUP_ASYNC_IO.SHORT_WAITS are a potential performance bottleneck when asynchronous I/O is used.

BCE

Reference: https://web.stanford.edu/dept/itss/docs/oracle/10gR2/backup.102/b14191/rcmtunin003.htm