Oracle当前联机日志组损坏的处理一oracle日志的特性总结1oracle日志切换规律（从最大sequence#号切换到最小sequence#号）eg如下所示：下个当前日志组会是sequenc
Oracle当前联机日志组损坏的处理
一oracle 日志的特性总结
1 oracle 日志切换规律（从最大sequence#号切换到最小sequence#号）
eg 如下所示：下个当前日志组会是sequence#号为27的5号日志组
SQL> select group#,archived,sequence#,status from v$log;
GROUP# ARC SEQUENCE# STATUS
---------- --- ---------- ----------------
1 NO 32 CURRENT
2 YES 28 INACTIVE
3 YES 29 INACTIVE
4 YES 30 INACTIVE
5 YES 27 INACTIVE <------众日志组中sequence#号最小
6 YES 31 INACTIVE
6 rows selected.
SQL> alter system switch logfile ;
System altered.
SQL> select group#,archived,sequence#,status from v$log;
GROUP# ARC SEQUENCE# STATUS
---------- --- ---------- ----------------
1 YES 32 ACTIVE
2 YES 28 INACTIVE
3 YES 29 INACTIVE
4 YES 30 INACTIVE
5 NO 33 CURRENT
6 YES 31 INACTIVE
6 rows selected.
2 快速转换oracle日志组状态active为inactive
日志组切换后，虚拟主机，上一个当前日志组状态由current变成active，实际上是由于当前数据文件头部的scn值还位于状态为active日志组的low scn 和next scn 内，所以我们此刻如果立即发起alter sytem checkpoint 命令推进数据文件头部scn 变可使日志状态由active 变为inactive。
SQL> select group#,archived,sequence#,status from v$log;
GROUP# ARC SEQUENCE# STATUS
---------- --- ---------- ----------------
1 YES 32 INACTIVE
2 YES 34 INACTIVE
3 YES 35 INACTIVE
4 NO 36 CURRENT
5 YES 33 INACTIVE
6 YES 31 INACTIVE
SQL> alter system switch logfile;
System altered.
SQL> select group#,archived,sequence#,status from v$log;
GROUP# ARC SEQUENCE# STATUS
---------- --- ---------- ----------------
1 YES 32 INACTIVE
2 YES 34 INACTIVE
3 YES 35 INACTIVE
4 YES 36 ACTIVE <------sequence号为36的日志为active
5 YES 33 INACTIVE
6 NO 37 CURRENT
6 rows selected.
查询数据文件头部scn情况如下：
SQL> select hxfil,fhscn from x$kcvfh;
HXFIL FHSCN
---------- ----------------
1 2781239221
2 2781239221
3 2781239221
4 2781239221
5 2781239221
6 2781239221
7 2781239221
8 2781239221
11 2781239221
12 2781239221
13 2781239221
SQL> select sequence#,first_change#,next_change# from v$log_history;
SEQUENCE# FIRST_CHANGE# NEXT_CHANGE#
---------- ------------- ------------
32 2781218249 2781218300
33 2781218300 2781219174
34 2781219174 2781219184
35 2781219184 2781239220
36 2781239220 2781239424
数据文件头部的scn：2781239221 处于sequence号为36的日志scn范围 内 2781239220 2781239424
SQL> alter system checkpoint;
System altered.
SQL> select hxfil,fhscn from x$kcvfh;
HXFIL FHSCN
---------- ----------------
1 2781239456
2 2781239456
3 2781239456
4 2781239456
5 2781239456
6 2781239456
7 2781239456
8 2781239456
11 2781239456
12 2781239456
13 2781239456
11 rows selected.
SQL> select group#,archived,sequence#,status from v$log;
GROUP# ARC SEQUENCE# STATUS
---------- --- ---------- ----------------
1 YES 32 INACTIVE
2 YES 34 INACTIVE
3 YES 35 INACTIVE
4 YES 36 INACTIVE
5 YES 33 INACTIVE
6 NO 37 CURRENT
3 clear 日志组的执行条件
clear的日志组状态不能是acitve 或者当前日志组
eg：
SQL> select group#,archived,sequence#,status from v$log;
GROUP# ARC SEQUENCE# STATUS
---------- --- ---------- ----------------
1 NO 38 CURRENT
2 YES 34 INACTIVE
3 YES 35 INACTIVE
4 YES 36 INACTIVE
5 YES 33 INACTIVE
6 YES 37 ACTIVE
SQL> alter database clear logfile group 6;
alter database clear logfile group 6
*
ERROR at line 1:
ORA-01624: log 6 needed for crash recovery of instance CRM (thread 1)
ORA-00312: online log 6 thread 1: '/oracle/CRM2/CRM/redo06.log'
ORA-00312: online log 6 thread 1: '/oracle/CRM2/CRM/redo06b.log'
二 数据库一直open当前联机日志组内成员全部损坏
此种情况最终就是日志不能切换，影响到数据库的应用时我们才可能发现。如下所示日志状态：
1 数据库日志状态如下：
SQL> select group#,archived,sequence#,status from v$log;
GROUP# ARC SEQUENCE# STATUS
---------- --- ---------- ----------------
1 NO 44 INACTIVE
2 NO 40 INACTIVE
3 NO 41 INACTIVE
4 NO 42 INACTIVE
5 NO 45 CURRENT
6 NO 43 INACTIVE
6 rows selected.
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