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.

Total number of bytes that will be read or written for the file, if known. If not known, this column will be null

Time the file was opened. If TYPE= AGGREGATE , then this is the time that the first file in the aggregate was opened

Time the file was closed. If TYPE= AGGREGATE , then this is the time that the last file in the aggregate was closed

Number of concurrently open DISK files. This value is only present in rows where TYPE= AGGREGATE .

Number of asynchronous requests for which a buffer was immediately ready for use

Number of times that a buffer was not immediately available, but a buffer became available after doing a nonblocking poll for I/O completion

Total time, in hundredths of a second, taken by nonblocking polls for I/O completion

Maximum time taken for a nonblocking poll for I/O completion, in hundredths of a second

The number of times that a buffer was not immediately available, and only became available after a blocking wait was issued

The total time, in hundredths of a second, taken by blocking waits for I/O completion

The maximum time taken for a blocking wait for I/O completion, in hundredths of a second

0: This value is used for rows containing data that pertain to the entire CDB. This value is also used for rows in non-CDBs.

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