Oracle 视图 V$DATAFILE 官方解释，作用，如何使用详细说明

网络编程 Oracle 视图 V$DATAFILE 官方解释，作用，如何使用详细说明 10-17

本站中文解释

一、关于Oracle视图
Oracle视图是Oracle数据库中只读的逻辑表，由一张或多张物理表的行和列组成，它可以被认为是一种物理表的虚拟映射，具有非常强大的功能。

二、V$DATAFILE视图介绍
V$DATAFILE视图显示实例归属的每个数据文件的当前信息。该视图存储在SGA中，运行中的实例可以实时查看数据库的信息，提供数据库实例浏览。

三、用途及如何使用
V$DATAFILE视图可以用来查看数据文件的名称，大小，当前状态等信息，查看数据文件是否正常工作。

通过Oracle之类SELECT * FROM V$DATAFILE 查看所得到的视图信息，若要更加有效的获取数据文件信息，可以使用Alter Database Command 命令：
例如：ALTER DATABASE DATAFILE ‘c:\oracle\oradata\mydb\mydata.dbf’ RESIZE 5M; 会把文件大小调整成5m，并强制运行中的数据库实例应用该变更。

官方英文解释

V$DATAFILE displays datafile information from the control file.

See Also:

“V$DATAFILE_HEADER”, which displays information from data file headers

Column	Datatype	Description
`FILE#`	`NUMBER`	Absolute file number
`CREATION_CHANGE#`	`NUMBER`	Change number at which the data file was created
`CREATION_TIME`	`DATE`	Timestamp of the data file creation
`TS#`	`NUMBER`	Tablespace number
`RFILE#`	`NUMBER`	Tablespace relative data file number
`STATUS`	`VARCHAR2(7)`	Type of file (system or user) and its status. Values: `OFFLINE`, `ONLINE`, `SYSTEM`, `RECOVER`, `SYSOFF` (an offline file from the `SYSTEM` tablespace)
`ENABLED`	`VARCHAR2(10)`	Describes how accessible the file is from SQL: `DISABLED` – No SQL access allowed `READ ONLY` – No SQL updates allowed `READ WRITE` – Full access allowed `UNKNOWN` – Unknown whether SQL updates would be allowed or not
`CHECKPOINT_CHANGE#`	`NUMBER`	SCN at last checkpoint
`CHECKPOINT_TIME`	`DATE`	Timestamp of the checkpoint#
`UNRECOVERABLE_CHANGE#`	`NUMBER`	Last unrecoverable change number made to this data file. If the database is in `ARCHIVELOG` mode, then this column is updated when an unrecoverable operation completes. If the database is not in `ARCHIVELOG` mode, this column does not get updated.
`UNRECOVERABLE_TIME`	`DATE`	Timestamp of the last unrecoverable change. This column is updated only if the database is in `ARCHIVELOG` mode.
`LAST_CHANGE#`	`NUMBER`	Last change number made to this data file (null if the data file is being changed)
`LAST_TIME`	`DATE`	Timestamp of the last change
`OFFLINE_CHANGE#`	`NUMBER`	Offline change number of the last offline range. This column is updated only when the data file is brought online.
`ONLINE_CHANGE#`	`NUMBER`	Online change number of the last offline range
`ONLINE_TIME`	`DATE`	Online timestamp of the last offline range
`BYTES`	`NUMBER`	Current data file size (in bytes); `0` if inaccessible
`BLOCKS`	`NUMBER`	Current data file size (in blocks); 0 if inaccessible
`CREATE_BYTES`	`NUMBER`	Size when created (in bytes)
`BLOCK_SIZE`	`NUMBER`	Block size of the data file
`NAME`	`VARCHAR2(513)`	Name of the data file
`PLUGGED_IN`	`NUMBER`	Describes whether the tablespace is plugged in. The value is `1` if the tablespace is plugged in and has not been made read/write, `0` if not.
`BLOCK1_OFFSET`	`NUMBER`	Offset from the beginning of the file to where the Oracle generic information begins. The exact length of the file can be computed as follows: `BYTES + BLOCK1_OFFSET`.
`AUX_NAME`	`VARCHAR2(513)`	Auxiliary name that has been set for this file via `CONFIGURE AUXNAME`
`FIRST_NONLOGGED_SCN`	`NUMBER`	First nonlogged SCN (check in standby database)
`FIRST_NONLOGGED_TIME`	`DATE`	First nonlogged time (check in standby database)
`FOREIGN_DBID`	`NUMBER`	Foreign DBID from which this data file came from. The value is 0 if this file is not a foreign database file.
`FOREIGN_CREATION_CHANGE#`	`NUMBER`	Creation SCN of a foreign data file. The value is 0 if this file is not a foreign database file.
`FOREIGN_CREATION_TIME`	`DATE`	Creation time of a foreign data file. The value is 0 if this file is not a foreign database file.
`PLUGGED_READONLY`	`VARCHAR2(3)`	`YES` if this is a transported read-only foreign file; otherwise `NO`.
`PLUGIN_CHANGE#`	`NUMBER`	SCN at which the foreign data file was transported into the database. The value is 0 if this file is not a foreign database file.
`PLUGIN_RESETLOGS_CHANGE#`	`NUMBER`	The SCN of the `RESETLOGS` operation for the incarnation into which this foreign file was transported. The value is 0 if this file is not a foreign database file.
`PLUGIN_RESETLOGS_TIME`	`DATE`	The time of the `RESETLOGS` operation for the incarnation into which this foreign file was transported. The value is 0 if this file is not a foreign database 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

编辑：一起学习网

标签：视图,实例,信息,文件,数据