V$BACKUP_ASYNC_IO displays performance information about ongoing and recently completed RMAN backups and restores. For each backup, it contains one row for each input datafile, one row for the aggregate total performance of all datafiles, and one row for the output backup piece. This data is not stored persistently, and is not preserved when the instance is re-started.
SID
Oracle SID of the session doing the backup or restore
SERIAL
Use count for the SID doing the backup or restore
USE_COUNT
A counter that can be used to identify rows from different backup sets
RMAN_STATUS_RECID
Owning V$RMAN_STATUS record ID
RMAN_STATUS_STAMP
Owning V$RMAN_STATUS record stamp
DEVICE_TYPE
Device type where the file is located
TYPE
INPUT, OUTPUT, or AGGREGATE
STATUS
NOT STARTED, IN PROGRESS, or FINISHED
FILENAME
Name of the backup file being read or written
SET_COUNT
Set count of the backup set being read or written
SET_STAMP
Set stamp of the backup set being read or written
BUFFER_SIZE
Size of the buffers being used to read/write the file, in bytes
BUFFER_COUNT
Number of buffers being used to read/write the file
TOTAL_BYTES
Total number of bytes that will be read or written for the file, if known. If not known, this column will be null
OPEN_TIME
Time the file was opened. If TYPE=’AGGREGATE’, then this is the time that the first file in the aggregate was opened
CLOSE_TIME
Time the file was closed. If TYPE=’AGGREGATE’, then this is the time that the last file in the aggregate was closed
ELAPSED_TIME
Time, in hundredths of a second, that the file was open
MAXOPENFILES
Number of concurrently open DISK files. This value is only present in rows where TYPE=’AGGREGATE’.
BYTES
Number of bytes read or written so far
EFFECTIVE_BYTES_PER_SECOND
I/O rate that was achieved with this device during this backup
IO_COUNT
Number of I/Os that were performed to this file
READY
Number of asynchronous requests for which a buffer was immediately ready for use
SHORT_WAITS
Number of times that a buffer was not immediately available, but a buffer became available after doing a nonblocking poll for I/O completion
SHORT_WAIT_TIME_TOTAL
Total time, in hundredths of a second, taken by nonblocking polls for I/O completion
SHORT_WAIT_TIME_MAX
Maximum time taken for a nonblocking poll for I/O completion, in hundredths of a second
LONG_WAITS
The number of times that a buffer was not immediately available, and only became available after a blocking wait was issued
LONG_WAIT_TIME_TOTAL
The total time, in hundredths of a second, taken by blocking waits for I/O completion
LONG_WAIT_TIME_MAX
The maximum time taken for a blocking wait for I/O completion, in hundredths of a second
