Oracle教程 2023-02-28

Oracle 视图 DBA_HIST_LOG 官方解释，作用，如何使用详细说明

本站中文解释

_FILES

Oracle中的视图DBA_HIST_LOG_FILES用于查看当前数据库中所有可用的日志文件大小(MB)及块大小(Bytes)。它是一个管理视图，提供了一个有效的方法来评估某台数据库所需日志空间大小，从而可以更好的预防数据库满日志文件的风险。

要使用DBA_HIST_LOG_FILES视图，首先要确定本地数据库的内部身份、标识符和路径，通过以下语句来查看：

SELECT MEMBER, THREAD#, LOG#, RESET#, RESETLOGS_TIME, BYTES
FROM DBA_HIST_LOG_FILES;

这条语句会返回当前数据库中所有归档日志文件的块大小(BYTES字段)、内部身份(MEMBER字段)、进程号(THREAD#字段)、日志号(LOG#字段)以及日志重建时间(RESETLOGS_TIME字段)。如果要查询当前数据库的每个日志文件的大小(MB)，可以将返回的BYTES字段除以1024 * 1024：

SELECT MEMBER LOG_SIZE_MB
FROM DBA_HIST_LOG_FILES
WHERE BYTES/(1024*1024)>0;

使用DBA_HIST_LOG_FILES视图可以帮助DBA更好的估算所需的日志文件空间，从而降低满日志文件或错误回滚的风险。

官方英文解释

DBA_HIST_LOG displays historical log file information from the control file. This view contains snapshots of V$LOG.

Column	Datatype	NULL	Description
`SNAP_ID`	`NUMBER`	`NOT NULL`	Unique snapshot ID
`DBID`	`NUMBER`	`NOT NULL`	Database ID for the snapshot
`INSTANCE_NUMBER`	`NUMBER`	`NOT NULL`	Instance number for the snapshot
`GROUP#`	`NUMBER`	`NOT NULL`	Log group number
`THREAD#`	`NUMBER`	`NOT NULL`	Log thread number
`SEQUENCE#`	`NUMBER`	`NOT NULL`	Log sequence number
`BYTES`	`NUMBER`		Size of the log (in bytes)
`MEMBERS`	`NUMBER`		Number of members in the log group
`ARCHIVED`	`VARCHAR2(3)`		Archive status (`YES`) or `NO`)
`STATUS`	`VARCHAR2(16)`		Log status: `UNUSED` – Online redo log has never been written to. This is the state of a redo log that was just added, or just after a `RESETLOGS`, when it is not the current redo log. `CURRENT` – Current redo log. This implies that the redo log is active. The redo log could be open or closed. `ACTIVE` – Log is active but is not the current log. It is needed for crash recovery. It may be in use for block recovery. It may or may not be archived. `CLEARING` – Log is being re-created as an empty log after an `ALTER DATABASE CLEAR LOGFILE` statement. After the log is cleared, the status changes to `UNUSED`. `CLEARING_CURRENT` – Current log is being cleared of a closed thread. The log can stay in this status if there is some failure in the switch such as an I/O error writing the new log header. `INACTIVE` – Log is no longer needed for instance recovery. It may be in use for media recovery. It may or may not be archived. `INVALIDATED` – Archived the current redo log without a log switch.
`FIRST_CHANGE#`	`NUMBER`		Lowest system change number (SCN) in the log
`FIRST_TIME`	`DATE`		Time of the first SCN in the log
`CON_DBID`	`NUMBER`		The database ID of the PDB for the sampled session
`CON_ID`	`NUMBER`		The ID of the container that `CON_DBID` identifies. 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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