V$LOG displays log file information from the control file.
| 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) |
| BLOCKSIZE | NUMBER | Block size of the logfile (512 or 4096) |
| 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 |
| NEXT_CHANGE# | NUMBER | Highest change number (SCN) in the log. When STATUS=CURRENT, NEXT_CHANGE# is set to the highest possible SCN, 281474976710655. |
| NEXT_TIME | DATE | Time of the highest SCN in the log. When STATUS=CURRENT, NEXT_TIME is set to NULL. |
- 这里面的sequence# 序列？这是什么意思？
sequence# 是日志的序列号- 还有凡是status为 当前的 ARC就是no
这个ARC代表着什么？ARC 代表是否已经归档 ，当前日志是不能归档的只有日志切换后，归档进程会将当前日志归档，下一个日志变为当前状态搜索- 最后first_change#是什么意思？表示这个日志中是从这个SCN号开始记录的
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