178.If a log file becomes corrupted, it may cause the database to stall. How would you correct such a situation?
A. Recover the online redo log from backup.
B. Delete and re-create the log file.
C. Use the alter database clear logfile command to clear the log file.
D. Shut down the database and restart it.
E. Shut down the database and then mount it. Clear the log file with the alter database clear logfile
command and then restart the database with alter database open resetlogs.
Answer: C答案解析：
sys@TEST1107> select * from v$log;
GROUP# THREAD# SEQUENCE# BYTES BLOCKSIZE MEMBERS ARC STATUS FIRST_CHANGE#
---------- ---------- ---------- ---------- ---------- ---------- --- ---------------- -------------
FIRST_TIME NEXT_CHANGE# NEXT_TIME
------------------ ------------ ------------------
1 1 0 52428800 512 2 YES UNUSED 1387129
07-NOV-13 1387224 07-NOV-13
2 1 26 52428800 512 2 YES INACTIVE 1387224
07-NOV-13 1387262 07-NOV-13
3 1 27 52428800 512 2 NO CURRENT 1387262
07-NOV-13 2.8147E+14
[oracle@rtest ~]$ rm -f /u01/app/oracle/oradata/test1107/redo02.log
sys@TEST1107> alter database clear logfile group 2;
Database altered.
----如果没有执行上面这个语句，在再次启动数据库时 被删掉的日志会变成INVALID状态。执行alter database clear logfile group 2，再次启动数据库时，日志都是正常的。
所以可以直接在线清除日志信息，E答案不用resetlogs打开数据库，错误。
D答案，再次启动，日志会变成INVALID状态。
B答案，需要关闭再起库到mount状态。
A答案，直接清除就可以，不需要恢复。
以下关闭再启库，只是测试日志是否正常。
sys@TEST1107> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
sys@TEST1107> startup
ORACLE instance started.
Total System Global Area 1269366784 bytes
Fixed Size 2227984 bytes
Variable Size 872415472 bytes
Database Buffers 385875968 bytes
Redo Buffers 8847360 bytes
Database mounted.
Database opened.
sys@TEST1107> select * from v$logfile;
GROUP# STATUS TYPE MEMBER IS_
---------- ------- ------- -------------------------------------------------- ---
3 ONLINE /u01/app/oracle/oradata/test1107/redo03.log NO
2 ONLINE /u01/app/oracle/oradata/test1107/redo02.log NO
1 ONLINE /u01/app/oracle/oradata/test1107/redo01.log NO
1 ONLINE /u01/app/oracle/oradata/test1107/redo01a.log NO
2 ONLINE /u01/app/oracle/oradata/test1107/redo02a.log NO
3 ONLINE /u01/app/oracle/oradata/test1107/redo03a.log NO
6 rows selected.