Oracle教程 2023-04-08

Oracle 视图 V$MAP_FILE 官方解释，作用，如何使用详细说明

V$MAP_FILE视图用于为SGA中每个文件记录其存在位置信息，只有undo文件和online redo log有映射文件，其它文件不需要。

V$MAP_FILE视图通常被用于检查数据库文件的状态，它可以提供有关各个文件的完整性写入和读取的信息，以及系统的性能信息，包括每次文件读取的耗时、写入的耗时和存储的页数。

如果要查看V$MAP_FILE视图的信息，可以使用如下SQL语句：

SELECT * FROM V$MAP_FILE;

V$MAP_FILE displays a list of all file mapping structures in the shared memory of the instance.

Column	Datatype	Description
`FILE_MAP_IDX`	`NUMBER`	Index corresponding to the file
`FILE_CFGID`	`VARCHAR2(256)`	Configuration ID (N/A if configuration ID is not supported)
`FILE_STATUS`	`VARCHAR2(7)`	Status of the mapping information: `VALID` – File mapping information is latest `INVALID` – Mapping must be refreshed
`FILE_NAME`	`VARCHAR2(256)`	Absolute file name
`FILE_TYPE`	`VARCHAR2(11)`	File type: `DATAFILE` `SPFILE` `TEMPFILE` `CONTROLFILE` `LOGFILE` `ARCHIVEFILE`
`FILE_STRUCTURE`	`VARCHAR2(9)`	File structure: `FILE` `RAWVOLUME` `RAWDEVICE` `NONE`
`FILE_SIZE`	`NUMBER`	File size in HKB (half KB)
`FILE_NEXTS`	`NUMBER`	Number of file extents in the file (not necessarily the same as the number of file extents mapped)
`LIB_IDX`	`NUMBER`	Index of mapping library claiming ownership of the file
`CON_ID`	`NUMBER`	The ID of the container to which the data pertains. Possible values include: `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. `1`: This value is used for rows containing data that pertain to only the root n: Where n is the applicable container ID for the rows containing data

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