Oracle 视图 V$BACKUP_ASYNC_IO 官方解释，作用，如何使用详细说明
本站中文解释
V$BACKUP_ASYNC_IO 是Oracle用于查询增量备份所使用的异步I/O（Asynchronous I/O）的视图。此视图可报告在备份的每一个文件上活动的异步I/O统计数据，它还能报告每一个备份位差异RMAN请求所需要的异步I/O次数。
使用方法：
1.查看指定文件号上活动异步I/O的信息：
SELECT * FROM V$BACKUP_ASYNC_IO where file#=&file;
2.查看指定备份位上所有文件号活动异步I/O的信息：
SELECT * FROM V$BACKUP_ASYNC_IO where thread# &thread;
3.查看每一个备份位差异RMAN请求所需要的异步I/O次数信息：
SELECT * FROM V$BACKUP_ASYNC_IO where diff#=&diff#;
官方英文解释
V$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 data file, one row for the aggregate total performance of all data files, 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 |
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Oracle SID of the session doing the backup or restore |
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Use count for the SID doing the backup or restore |
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A counter that can be used to identify rows from different backup sets |
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Owning |
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Owning |
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Device type where the file is located |
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Name of the backup file being read or written |
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Set count of the backup set being read or written |
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Set stamp of the backup set being read or written |
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Size of the buffers being used to read/write the file, in bytes |
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Number of buffers being used to read/write the file |
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Total number of bytes that will be read or written for the file, if known. If not known, this column will be null |
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Time the file was opened. If |
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Time the file was closed. If |
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Time, in hundredths of a second, that the file was open |
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Number of concurrently open DISK files. This value is only present in rows where |
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Number of bytes read or written so far |
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I/O rate that was achieved with this device during this backup |
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Number of I/Os that were performed to this file |
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Number of asynchronous requests for which a buffer was immediately ready for use |
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Number of times that a buffer was not immediately available, but a buffer became available after doing a nonblocking poll for I/O completion |
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Total time, in hundredths of a second, taken by nonblocking polls for I/O completion |
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Maximum time taken for a nonblocking poll for I/O completion, in hundredths of a second |
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The number of times that a buffer was not immediately available, and only became available after a blocking wait was issued |
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The total time, in hundredths of a second, taken by blocking waits for I/O completion |
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The maximum time taken for a blocking wait for I/O completion, in hundredths of a second |
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The ID of the container to which the data pertains. Possible values include:
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