Q
题目
在Oracle中，数据文件OFFLINE之后必须要做的一件事是什么？
A
答案
数据文件OFFLINE之后必须要做的一件事就是立刻执行一次RECOVER操作，这样在无论过了多久之后，在ONLINE该数据文件的时候就不需要执行RECOVER操作了。
下面通过两个实验来对比验证该结论。
实验环境如下表所示：
项目 | source db |
|---|---|
db 类型 | 单实例 |
db version | 11.2.0.3.4 |
db 存储 | ASM |
OS版本及kernel版本 | AIX 64位 7.1.0.0 |
实验一：数据文件OFFLINE后没有立刻执行RECOVER操作
代码语言：javascript复制SYS@lhrdb> COL NAME FOR A60
SYS@lhrdb> SELECT FILE#,NAME,STATUS FROM V$DATAFILE;
FILE# NAME STATUS
---------- ------------------------------------------------------------ -------
1 DATA/lhrdb/datafile/system.347.916601927 SYSTEM
2 DATA/lhrdb/datafile/sysaux.340.916601927 ONLINE
3 DATA/lhrdb/datafile/undotbs1.353.916601927 ONLINE
4 DATA/lhrdb/datafile/users.445.916601927 ONLINE
5 DATA/lhrdb/datafile/example.416.916602001 ONLINE
6 DATA/lhrdb/datafile/ts_mig_chain_lhr.471.919677645 ONLINE
6 rows selected.
SYS@lhrdb> ALTER DATABASE DATAFILE 6 OFFLINE;
ALTER DATABASE DATAFILE 6 OFFLINE
*
ERROR at line 1:
ORA-01145: offline immediate disallowed unless media recovery enabled
====>>>>> 数据库必须归档才可以OFFLINE
SYS@lhrdb> ARCHIVE LOG LIST;
Database log mode No Archive Mode
Automatic archival Disabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 265
Current log sequence 267
SYS@lhrdb> SHUTDOWN IMMEDIATE
Database closed.
Database dismounted.
ORACLE instance shut down.
SYS@lhrdb> STARTUP MOUNT
ORACLE instance started.
Total System Global Area 1720328192 bytes
Fixed Size 2247072 bytes
Variable Size 486540896 bytes
Database Buffers 1224736768 bytes
Redo Buffers 6803456 bytes
Database mounted.
SYS@lhrdb> ALTER DATABASE ARCHIVELOG;
Database altered.
SYS@lhrdb> ALTER DATABASE OPEN;
Database altered.
SYS@lhrdb> ALTER DATABASE DATAFILE 6 OFFLINE;
Database altered.
SYS@lhrdb> SELECT FILE#,NAME,STATUS FROM V$DATAFILE;
FILE# NAME STATUS
---------- ------------------------------------------------------------ -------
1 DATA/lhrdb/datafile/system.347.916601927 SYSTEM
2 DATA/lhrdb/datafile/sysaux.340.916601927 ONLINE
3 DATA/lhrdb/datafile/undotbs1.353.916601927 ONLINE
4 DATA/lhrdb/datafile/users.445.916601927 ONLINE
5 DATA/lhrdb/datafile/example.416.916602001 ONLINE
6 DATA/lhrdb/datafile/ts_mig_chain_lhr.471.919677645 RECOVER
6 rows selected.
SYS@lhrdb> SELECT FILE#,ONLINE_STATUS,CHANGE#,ERROR FROM V$RECOVER_FILE;
FILE# ONLINE_ CHANGE# ERROR
---------- ------- ---------- -----------------------------------------------------------------
6 OFFLINE 7485831
SYS@lhrdb> ALTER SYSTEM SWITCH LOGFILE;
System altered.
SYS@lhrdb> ALTER SYSTEM SWITCH LOGFILE;
System altered.
SYS@lhrdb> ALTER DATABASE DATAFILE 6 ONLINE;
alter database datafile 6 online
*
ERROR at line 1:
ORA-01113: file 6 needs media recovery
ORA-01110: data file 6: ' DATA/lhrdb/datafile/ts_mig_chain_lhr.471.919677645'
SYS@lhrdb> RECOVER DATAFILE 6;
Media recovery complete.
SYS@lhrdb> ALTER DATABASE DATAFILE 6 ONLINE;<<<<<<<<<----- 可以看到6号文件必须先执行recover操作后才能执行ONLINE
Database altered.
实验二：数据文件OFFLINE后立刻执行一次RECOVER操作
代码语言：javascript复制SYS@lhrdb> ALTER DATABASE DATAFILE 6 OFFLINE;
Database altered.
SYS@lhrdb> recover datafile 6;<<<<<<<<<----- OFFLINE后接着执行recover操作
Media recovery complete.
SYS@lhrdb> SELECT FILE#,ONLINE_STATUS,CHANGE#,ERROR FROM V$RECOVER_FILE;<<<<<<<<<--该视图查不到数据
no rows selected
SYS@lhrdb> SELECT FILE#,NAME,STATUS FROM V$DATAFILE;
FILE# NAME STATUS
---------- ------------------------------------------------------------ -------
1 DATA/lhrdb/datafile/system.347.916601927 SYSTEM
2 DATA/lhrdb/datafile/sysaux.340.916601927 ONLINE
3 DATA/lhrdb/datafile/undotbs1.353.916601927 ONLINE
4 DATA/lhrdb/datafile/users.445.916601927 ONLINE
5 DATA/lhrdb/datafile/example.416.916602001 ONLINE
6 DATA/lhrdb/datafile/ts_mig_chain_lhr.471.919677645 OFFLINE
6 rows selected.
SYS@lhrdb> ALTER SYSTEM SWITCH LOGFILE;
System altered.
SYS@lhrdb> ALTER SYSTEM SWITCH LOGFILE;
System altered.
SYS@lhrdb> ALTER SYSTEM SWITCH LOGFILE;
System altered.
SYS@lhrdb> alter database datafile 6 online;<<<<<<<<<-----切换日志后让数据文件做ONLINE操作并不需要执行RECOVER操作
Database altered.
SYS@lhrdb> select file#,name,status from v$datafile;
FILE# NAME STATUS
---------- ------------------------------------------------------------ -------
1 DATA/lhrdb/datafile/system.347.916601927 SYSTEM
2 DATA/lhrdb/datafile/sysaux.340.916601927 ONLINE
3 DATA/lhrdb/datafile/undotbs1.353.916601927 ONLINE
4 DATA/lhrdb/datafile/users.445.916601927 ONLINE
5 DATA/lhrdb/datafile/example.416.916602001 ONLINE
6 DATA/lhrdb/datafile/ts_mig_chain_lhr.471.919677645 ONLINE
6 rows selected.
SYS@lhrdb>
实验结束，根据实验过程可以知道，如果执行了数据文件的OFFLINE操作，那么需要接着执行一次RECOVER操作。这样做的好处是，在以后的数据库维护中，随时想将数据文件ONLINE都可以，而不用担心归档文件是否存在的情况了。
& 说明：
有关本小节内容可以参考我的BLOG：http://blog.itpub.net/26736162/viewspace-2125336/
