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V$BACKUP_SYNC_IO displays performance information about ongoing and recently completed RMAN backups and restores. For each backup, it contains one row for each input datafile, one row for the aggregate total performance of all datafiles, and one row for the output backup piece. This data is not stored persistently, and is not preserved when the instance is re-started.
Column | Datatype | Description |
SID | NUMBER | The Oracle SID of the session doing the backup or restore |
SERIAL | NUMBER | The use count for the SID doing the backup or restore |
USE_COUNT | NUMBER | A counter that can be used to identify rows from different backup sets |
RMAN_STATUS_RECID | NUMBER | Owning V$RMAN_STATUS record ID |
RMAN_STATUS_STAMP | NUMBER | Owning V$RMAN_STATUS record stamp |
DEVICE_TYPE | VARCHAR2(17) | The device type where the file is located |
TYPE | VARCHAR2(9) | INPUT, OUTPUT, or AGGREGATE |
STATUS | VARCHAR2(11) | NOT STARTED, IN PROGRESS, or FINISHED |
FILENAME | VARCHAR2(513) | The name of the backup file being read or written |
SET_COUNT | NUMBER | The set count of the backup set being read or written |
SET_STAMP | NUMBER | The set stamp of the backup set being read or written |
BUFFER_SIZE | NUMBER | The size of the buffers being used to read/write this file, in bytes |
BUFFER_COUNT | NUMBER | The number of buffers being used to read/write this file |
TOTAL_BYTES | NUMBER | The total number of bytes that will be read or written for this file, if known. If not known, this column will be null. |
OPEN_TIME | DATE | The time this file was opened. If TYPE='AGGREGATE', then this is the time that the first file in the aggregate was opened. |
CLOSE_TIME | DATE | The time this file was closed. If TYPE='AGGREGATE', then this is the time that the last file in the aggregate was closed. |
ELAPSED_TIME | NUMBER | The time, in hundredths of a second, that the file was open |
MAXOPENFILES | NUMBER | The number of concurrently open DISK files. This value is only present in rows where TYPE='AGGREGATE'. |
BYTES | NUMBER | The number of bytes read or written so far |
EFFECTIVE_BYTES_PER_SECOND | NUMBER | The I/O rate that was achieved with this device during this backup |
IO_COUNT | NUMBER | The number of I/Os that were performed to this file |
IO_TIME_TOTAL | NUMBER | The total time, in hundredths of a second, taken to do I/O for this file |
IO_TIME_MAX | NUMBER | The maximum time taken for a single I/O request |
DISCRETE_BYTES_PER_SECOND | NUMBER | The average transfer rate for this file |
Note:
1. V$BACKUP_ASYNC_IO and V$BACKUP_SYNC_IO can be used to determine the source of backup or restore bottlenecks and to see detailed progress of backup jobs. V$BACKUP_SYNC_IO contains rows when the I/O is synchronous to the process / thread performing the backup. V$BACKUP_ASYNC_IO contains rows when the I/O is asynchronous.
2. EFFECTIVE_BYTES_PER_SECOND column in V$BACKUP_ASYNC_IO and V$BACKUP_SYNC_IO can be used to determine whether the tape is streaming when the I/O is synchronous. If EFFECTIVE_BYTES_PER_SECOND is less than the raw capacity of the hardware, then the tape is not streaming. If EFFECTIVE_BYTES_PER_SECOND is greater than the raw capacity of the hardware, the tape may or may not be streaming. Compression may cause the EFFECTIVE_BYTES_PER_SECOND to be greater than the speed of real I/O.
3. It is difficult to identify bottleneck with synchronous I/O because all synchronous I/O is bottleneck to the process. The DISCRETE_BYTES_PER_SECOND column displays the I/O rate. If you see data in V$BACKUP_SYNC_IO, then the problem is that you have not enabled asynchronous I/O or you are not using disk I/O slaves.
Oracle data dictionary views
Last updated: 2009-12-09 Wednesday |
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