oracle如何重做日志组
1、查询数据库中的重做日志组
SQL> select * from v$log;
GROUP# THREAD# SEQUENCE# BYTES BLOCKSIZE MEMBERS ARC STATUS FIRST_CHANGE# FIRST_TIM NEXT_CHANGE# NEXT_TIME
1 1 64 52428800 512 1 NO CURRENT 1522229 17-MAY-19 2.8147E+14
2 1 62 52428800 512 1 NO INACTIVE 1502072 16-MAY-19 1515210 17-MAY-19
3 1 63 52428800 512 1 NO INACTIVE 1515210 17-MAY-19 1522229 17-MAY-19
2、具体查看日志文件详情(位置)
SQL> select * from v$logfile;
GROUP# STATUS TYPE MEMBER IS_RECOVERY_DEST_FILE
3 ONLINE /u01/app/oraData/orcl/redo03.log NO
2 ONLINE /u01/app/oraData/orcl/redo02.log NO
1 ONLINE /u01/app/oraData/orcl/redo01.log NO
3、创建重做日志组
SQL> alter database add logfile ('/u01/app/oraData/orcl/hbk01.rdo','/u01/app/oraData/orcl/hbk02.rdo') size 5M;
Database altered.
SQL> select * from v$logfile;
GROUP# STATUS TYPE MEMBER IS_RECOVERY_DEST_FILE
3 ONLINE /u01/app/oraData/orcl/redo03.log NO
2 ONLINE /u01/app/oraData/orcl/redo02.log NO
1 ONLINE /u01/app/oraData/orcl/redo01.log NO
4 ONLINE /u01/app/oraData/orcl/hbk01.rdo NO
4 ONLINE /u01/app/oraData/orcl/hbk02.rdo NO
可以看到多了两个重做日志文件hbk01.rdo,hbk02.rdo，组的编号为4,查询v$log可以知道4号组的status为UNUSED，表示新建状态，未使用。
SQL> select * from v$log;
GROUP# THREAD# SEQUENCE# BYTES BLOCKSIZE MEMBERS ARC STATUS FIRST_CHANGE# FIRST_TIM NEXT_CHANGE# NEXT_TIME
1 1 64 52428800 512 1 NO CURRENT 1522229 17-MAY-19 2.8147E+14
2 1 62 52428800 512 1 NO INACTIVE 1502072 16-MAY-19 1515210 17-MAY-19
3 1 63 52428800 512 1 NO INACTIVE 1515210 17-MAY-19 1522229 17-MAY-19
4 1 0 5242880 512 2 YES UNUSED 0 0
可以看出我们创建重做日志组的编号默认系统产生
我们也可以知道组编号
SQL> alter database add logfile group 8 ('/u01/app/oraData/orcl/hbk10.rdo') size 5M;
Database altered.
SQL> select * from v$logfile;
GROUP# STATUS TYPE MEMBER IS_RECOVERY_DEST_FILE
4、删除重做日志组
删除重做日志组只是更新了控制文件，被删除的组所拥有的重做日志文件并没有从操作系统中删除，需要手工删除，而且只能删除状态是INAVTIVE的重做日志组，如果想删除当前(CURRENT)的重做日志组，必须手工切换，可以使用alter system switch logfile,而且每个数据库至少需要有两组重做日志组，因为要循环使用。
删除之前先查询下
SQL> select group#,status from v$log;
GROUP# STATUS
1 CURRENT
2 INACTIVE
3 INACTIVE
4 UNUSED
8 UNUSED
像组2和组3都可以删，而组1为当前使用，不能删，除非切换使用日志组。删除之前先记下文件位置，方便手动执行操作系统rm删除命令
alter database drop logfile group 2;
5、删除日志成员
需要注意的是，一个日志组中至少需要保留一个成员，而且只能删除状态不是ONLINE或CURRENT的日志成员。
SQL> select * from v$logfile;无锡正规妇科 http://www.xasgyy.net/
GROUP# STATUS TYPE MEMBER IS_RECOVERY_DEST_FILE
SQL> alter database drop logfile member '/u01/app/oraData/orcl/hbk10.rdo';
alter database drop logfile member '/u01/app/oraData/orcl/hbk10.rdo'
ERROR at line 1:
ORA-00362: member is required to form a valid logfile in group 8
ORA-01517: log member: '/u01/app/oraData/orcl/hbk10.rdo'
SQL> alter database drop logfile member '/u01/app/oraData/orcl/hbk8.rdo';
Database altered.
7、查看重做日志是否归档
SQL> select group#,status,archived from v$log;
GROUP# STATUS ARC
1 INACTIVE NO
2 INACTIVE NO
3 INACTIVE NO
4 INACTIVE NO
8 CURRENT NO
NO表示未归档，YES表示已归档。
因为我的没有开启归档模式，所以都显示NO
SQL> select name,log_mode from v$database;
NAME LOG_MODE
ORCL NOARCHIVELOG
