利用omf来管理联机重做日志文件

利用Oracle管理文件来自动管理和维护重做日志文件是Oracle9i开始引入的。

例如：

SQL> alter system set DB_CREATE_ONLINE_LOG_DEST_1='/oradata/law/law';

System altered.

SQL> alter system set DB_CREATE_ONLINE_LOG_DEST_2='/oradata/law/law';

System altered.

SQL> alter database add logfile;

Database altered.

SQL> select group#,sequence#,members,bytes/1024/1024 MB,status from v$log;

GROUP#  SEQUENCE#    MEMBERS         MB STATUS

------ ---------- ---------- ---------- ----------------

     1          8          2         50 CURRENT

     2          6          2         50 INACTIVE

     3          0          1         50 UNUSED

     4          0          2        100 UNUSED

SQL> select * from v$logfile;

GROUP# STATUS  TYPE    MEMBER                    IS_

------ ------- ------- ------------------------- ---

     3         ONLINE  /oradata/law/law/redo03.l NO

                       og

     2 STALE   ONLINE  /oradata/law/law/redo02.l NO

                       og

     1         ONLINE  /oradata/law/law/redo01.l NO

                       og

     1 INVALID ONLINE  /oradata/law/law/redo01a. NO

                       log

     2 INVALID ONLINE  /oradata/law/law/redo02a. NO

                       log

     4         ONLINE  /oradata/law/law/LAW/onli NO

                       nelog/o1_mf_4_8xt082pr_.l

                       og

     4         ONLINE  /oradata/law/law/LAW/onli NO

                       nelog/o1_mf_4_8xt0888c_.l

                       og

7 rows selected.

SQL> alter database drop logfile group 4;

Database altered.

SQL> select group#,sequence#,members,bytes/1024/1024,status,archived

  2  from v$log;

GROUP#  SEQUENCE#    MEMBERS BYTES/1024/1024 STATUS           ARC

------ ---------- ---------- --------------- ---------------- ---

     1          8          2              50 CURRENT          NO

     2          6          2              50 INACTIVE         NO

     3          0          1              50 UNUSED           NO

SQL> select * from v$logfile;

GROUP# STATUS  TYPE    MEMBER                    IS_

------ ------- ------- ------------------------- ---

     3         ONLINE  /oradata/law/law/redo03.l NO

                       og

     2 STALE   ONLINE  /oradata/law/law/redo02.l NO

                       og

     1         ONLINE  /oradata/law/law/redo01.l NO

                       og

     1 INVALID ONLINE  /oradata/law/law/redo01a. NO

                       log

     2 INVALID ONLINE  /oradata/law/law/redo02a. NO

                       log

OMF管理的方式:在删除日志文件后，操作系统上的日子文件也同时被删除。