日誌相關介紹......
查看日誌的工作狀態信息
select * from v$log;GROUP# THREAD# SEQUENCE# BYTES BLOCKSIZE MEMBERS ARCHIVED STATUS FIRST_CHANGE# FIRST_TIME NEXT_CHANGE# NEXT_TIME
1 1 52 52428800 512 2 NO CURRENT 1314820 2018/5/3 02:38:18 281474976710655
2 1 50 52428800 512 2 NO INACTIVE 1295249 2018/5/2 13:56:43 1311962 2018/5/3 01:01:09
3 1 51 52428800 512 2 NO ACTIVE 1311962 2018/5/3 01:01:09 1314820 2018/5/3 02:38:18
Elapsed: 00:00:00.03查看日誌文件物理信息
select * from v$logfile; GROUP# STATUS TYPE MEMBER IS_
---------- ------- ------- ---------------------------------------------------------------------- ---
3 ONLINE +DATA/sundb/onlinelog/group_3.263.974086789 NO
3 ONLINE +FLASH/sundb/onlinelog/group_3.259.974086789 YES
2 ONLINE +DATA/sundb/onlinelog/group_2.262.974086785 NO
2 ONLINE +FLASH/sundb/onlinelog/group_2.258.974086787 YES
1 ONLINE +DATA/sundb/onlinelog/group_1.261.974086783 NO
1 ONLINE +FLASH/sundb/onlinelog/group_1.257.974086785 YES
6 rows selected.
Elapsed: 00:00:00.01切換日誌文件
alter system switch logfile;GROUP# THREAD# SEQUENCE# BYTES BLOCKSIZE MEMBERS ARCHIVED STATUS FIRST_CHANGE# FIRST_TIME NEXT_CHANGE# NEXT_TIME
1 1 52 52428800 512 2 NO INACTIVE 1314820 2018/5/3 2:38:18 1314948 2018/5/3 2:44:24
2 1 53 52428800 512 2 NO CURRENT 1314948 2018/5/3 2:44:24 281474976710655
3 1 51 52428800 512 2 NO INACTIVE 1311962 2018/5/3 1:01:09 1314820 2018/5/3 2:38:18
查看日誌切換歷史數據
select to_char(first_time,'yyyymmddhh24'),count(1) from v$log_history group by to_char(first_time,'yyyymmddhh24') order by to_char(first_time,'yyyymmddhh24');TO_CHAR(FI COUNT(1)
---------- ----------
2018042203 3
2018042205 1
2018042301 1
2018042723 1
2018050122 1
2018050212 10
2018050213 33
2018050301 1
2018050302 1
9 rows selected.
Elapsed: 00:00:00.01Oracle建議日誌切換時間爲15分鐘到30分鐘
調整日誌切換頻率：增加組的數量、增加成員的大小
查看日誌成員
select * from v$logfile;GROUP# STATUS TYPE MEMBER IS_RECOVERY_DEST_FILE
3 ONLINE +DATA/sundb/onlinelog/group_3.263.974086789 NO
3 ONLINE +FLASH/sundb/onlinelog/group_3.259.974086789 YES
2 ONLINE +DATA/sundb/onlinelog/group_2.262.974086785 NO
2 ONLINE +FLASH/sundb/onlinelog/group_2.258.974086787 YES
1 ONLINE +DATA/sundb/onlinelog/group_1.261.974086783 NO
1 ONLINE +FLASH/sundb/onlinelog/group_1.257.974086785 YES
alter database add logfile '+DATA/' size 100m;select * from v$log;GROUP# THREAD# SEQUENCE# BYTES BLOCKSIZE MEMBERS ARCHIVED STATUS FIRST_CHANGE# FIRST_TIME NEXT_CHANGE# NEXT_TIME
1 1 52 52428800 512 2 NO INACTIVE 1314820 2018/5/3 2:38:18 1314948 2018/5/3 2:44:24
2 1 53 52428800 512 2 NO CURRENT 1314948 2018/5/3 2:44:24 281474976710655
3 1 51 52428800 512 2 NO INACTIVE 1311962 2018/5/3 1:01:09 1314820 2018/5/3 2:38:18
4 1 0 104857600 512 1 YES UNUSED 0 0
alter database add logfile member '+FLASH/' to group 4;select * from v$logfile;GROUP# STATUS TYPE MEMBER IS_RECOVERY_DEST_FILE
3 ONLINE +DATA/sundb/onlinelog/group_3.263.974086789 NO
3 ONLINE +FLASH/sundb/onlinelog/group_3.259.974086789 YES
2 ONLINE +DATA/sundb/onlinelog/group_2.262.974086785 NO
2 ONLINE +FLASH/sundb/onlinelog/group_2.258.974086787 YES
1 ONLINE +DATA/sundb/onlinelog/group_1.261.974086783 NO
1 ONLINE +FLASH/sundb/onlinelog/group_1.257.974086785 YES
4 ONLINE +DATA/sundb/onlinelog/group_4.275.975121115 NO
4 INVALID ONLINE +FLASH/sundb/onlinelog/group_4.260.975121483 NO
刪除成員
alter database drop logfile member '+FLASH/sundb/onlinelog/group_4.260.975121483';GROUP# STATUS TYPE MEMBER IS_RECOVERY_DEST_FILE
3 ONLINE +DATA/sundb/onlinelog/group_3.263.974086789 NO
3 ONLINE +FLASH/sundb/onlinelog/group_3.259.974086789 YES
2 ONLINE +DATA/sundb/onlinelog/group_2.262.974086785 NO
2 ONLINE +FLASH/sundb/onlinelog/group_2.258.974086787 YES
1 ONLINE +DATA/sundb/onlinelog/group_1.261.974086783 NO
1 ONLINE +FLASH/sundb/onlinelog/group_1.257.974086785 YES
4 ONLINE +DATA/sundb/onlinelog/group_4.275.975121115 NO刪除日誌組
alter database drop logfile group 4;GROUP# STATUS TYPE MEMBER IS_RECOVERY_DEST_FILE
3 ONLINE +DATA/sundb/onlinelog/group_3.263.974086789 NO
3 ONLINE +FLASH/sundb/onlinelog/group_3.259.974086789 YES
2 ONLINE +DATA/sundb/onlinelog/group_2.262.974086785 NO
2 ONLINE +FLASH/sundb/onlinelog/group_2.258.974086787 YES
1 ONLINE +DATA/sundb/onlinelog/group_1.261.974086783 NO
1 ONLINE +FLASH/sundb/onlinelog/group_1.257.974086785 YES刪除成員的限制：當前組不能刪，每組最後一個成員不能刪，
刪除組的限制：當前組不能刪，活動組不能刪，如果數據庫只剩下兩組日誌，任何一組都不能被刪除
由於redo log在切換的時候就會把數據覆蓋掉，如果想把數據庫的改變記錄下來，可以使用數據庫的歸檔模式，在歸檔模式下，當聯機日誌進行切換的時候，當前組的內容都會被歸檔進程做一個鏡像備份並生成歸檔文件。
將數據庫變爲歸檔模式
查看當前數據庫歸檔信息
archive log listDatabase log mode No Archive Mode
Automatic archival Disabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 51
Current log sequence 53正常關閉數據庫
shut immediate啓動數據庫到MOUNT狀態
startup mount將數據庫更改爲歸檔模式
alter database archivelog;打開數據庫
alter database open；查看歸檔信息
archive log listDatabase log mode Archive Mode
Automatic archival Enabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 51
Next log sequence to archive 53
Current log sequence 53切換日誌文件，生成歸檔文件
alter system switch logfile;select sequence#,name from v$archived_log;SEQUENCE# NAME
53 +FLASH/sundb/archivelog/2018_05_03/thread_1_seq_53.260.975122575