redo log

1.redo log相关数据字典

v$log:display the redo log file information from the control file

v$logfile:identifies redo log group# and members and memeber status

v$log_history:contains log history information

2.v$log

Column	Datatype	Description
GROUP#	NUMBER	Log group number
THREAD#	NUMBER	Log thread number
SEQUENCE#	NUMBER	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.
FIRST_CHANGE#	NUMBER	Lowest system change number (SCN) in the log
FIRST_TIME	DATE	Time of the first SCN in the log

3.V$LOGFILE 

Column	Datatype	Description
GROUP#	NUMBER	Redo log group identifier number
STATUS	VARCHAR2(7)	Status of the log member: INVALID - File is inaccessible STALE - File's contents are incomplete DELETED - File is no longer used null - File is in use
TYPE	VARCHAR2(7)	Type of the logfile: ONLINE STANDBY
MEMBER	VARCHAR2(513)	Redo log member name
IS_RECOVERY_DEST_FILE	VARCHAR2(3)	Indicates whether the file was created in the flash recovery area (YES) or not (NO)