一、什么是ControlFile
Control file体积虽小（主要由createdatabase的命令决定），但起到了很重要的作用，它定义了当前物理数据库的状态，并对数据库进行维护和管理。在启动数据库时进入mount状态需要使用control file。一个数据库对应一个control file，如果丢失了可能可以恢复。
[oracle@localhost ~]$ cd $ORACLE_HOME/dbs
[oracle@localhost dbs]$ strings spfileorcl.ora | more
orcl.__db_cache_size=96468992 orcl.__java_pool_size=4194304 orcl.__large_pool_size=4194304 ... *.control_files='/oracle/oradata/orcl/control01.ctl','/oracle/flash_recovery_area/o rcl/control02.ctl' # 这里定义了控制文件的位置 *.dispatchers='(PROTOCOL=TCP) (SERVICE=orclXDB)'
[oracle@localhost dbs]$ cd /oracle/oradata/orcl
[oracle@localhost orcl]$ ls
control01.ctl redo01.log redo03.log system01.dbf undotbs01.dbf # 根据SPFILE定义的路径可以找到control file example01.dbf redo02.log sysaux01.dbf temp01.dbf users01.dbf
二、数据库启动过程中ControlFile的作用
Nomount状态不需要用到controlfile
Mount状态会根据PFILE或SPFILE中定义的路径打开control file，将其读入内存，然后根据control file获取数据文件的名字、状态和redo log files的相关信息
OPEN状态主要是读取一些体积较大的文件。
[oracle@localhost orcl]$ strings control01.ctl | more
/oracle/oradata/orcl/redo03.log ... /oracle/oradata/orcl/sysaux01.dbf /oracle/oradata/orcl/example01.dbf
三、ControlFile的复用
关于ControlFile的说明，可以查阅联机文档中concept 和Administrator'sGuide的相关章节。
如果在初始化参数文件中定义了多个controlfiles（最多可以定义8个文件），那么oracle写信息时会同时向多个文件中写入数据，但是读数据时只读第一个文件。如果控制文件中的任何一个损坏了，则整个实例都无法操作了，这点和联机重做日志不一样。
Oracle强烈建议最好准备两个以上的controlfile，并存放在不同的磁盘上。
如何进行ControlFile的多路复用呢：
1. 使用SPFILE复用Control File
[oracle@localhost ~]$ sqlplus /nolog
SQL*Plus: Release 11.2.0.1.0 Production on Tue Sep 923:25:46 2014 Copyright (c) 1982, 2009, Oracle. All rights reserved.
SQL> conn / assysdba
Connected. SQL> showparameter control NAME TYPE VALUE ------------------------------------ ------------------------------------------------------------------------------- control_file_record_keep_time integer 7 control_files string /oracle/oradata/orcl/control01.ctl, /oracle/flash_recovery_area/orcl/control02.ctl control_management_pack_access string DIAGNOSTIC+TUNING -- 查看当前control file的位置
SQL> alter system
setcontrol_files='/oracle/oradata/orcl/control01.ctl','/oracle/flash_recovery_area/orcl/control02.ctl','/oracle/oradata/orcl/control03.ctl'scope=spfile; -- 修改SPFILE System altered.
SQL> shutdown immediate
Database closed. Database dismounted. ORACLE instance shut down. -- 关闭数据库
[oracle@localhost dbs]$ strings spfileorcl.ora | more
orcl.__db_cache_size=96468992 orcl.__java_pool_size=4194304 ... *.compatible='11.2.0.0.0' *.control_files='/oracle/oradata/orcl/control01.ctl','/oracle/flash_recovery_area/o rcl/control02.ctl','/oracle/oradata/orcl/control03.ctl' # 可以看到SPFILE已经被修改了
[oracle@localhost dbs]$ cd /oracle/oradata/orcl
[oracle@localhost orcl]$ ls
control01.ctl redo01.log redo03.log system01.dbf undotbs01.dbf example01.dbf redo02.log sysaux01.dbf temp01.dbf users01.dbf
[oracle@localhost orcl]$ cp control01.ctl ./control03.ctl
# 复制一份control file
SQL> startup
-- 重新启动数据库 ORACLE instance started. Total System Global Area 422670336 bytes Fixed Size 1336960 bytes Variable Size 318769536 bytes Database Buffers 96468992 bytes Redo Buffers 6094848 bytes Database mounted. Database opened.
SQL> showparameter control
NAME TYPE VALUE ------------------------------- ---------------------------------- control_file_record_keep_time integer 7 control_files string /oracle/oradata/orcl/control01.ctl , /oracle/flash_recovery_area/orcl /control02.ctl, /oracle/oradata/orcl/control03.ctl -- 再次查看，会发现多了一个control file control_management_pack_access string DIAGNOSTIC+TUNING
2. 使用SPFILE复用Control File
使用PFILE和SPFILE 方法类似，只不过启动时指定特定的PFILE即可
SQL> createpfile from spfile;
-- 通过PFILE创建SPFILE File created.
SQL> shutdownimmediate
Database closed. Database dismounted. ORACLE instance shut down. -- 关闭数据库
[oracle@localhost ~]$ cd /oracle/11g/dbs
[oracle@localhost dbs]$ ls
crdb01.sql hc_orcl.dat kWLY old peshm_smn_0 wly.env ... spfileorcl.ora initorcl.ora
[oracle@localhost dbs]$ vim initorcl.ora
orcl.__db_cache_size=96468992 ... *.compatible='11.2.0.0.0' *.control_files='/oracle/oradata/orcl/control01.ctl','/oracle/flash_recovery_area/orcl/control02.ctl','/oracle/oradata/orcl/control03.ctl','/oracle/oradata/orcl/control04.ctl' # 在新建的PFILE中添加control04.ctl *.db_block_size=8192 ... *.dispatchers='(PROTOCOL=TCP) (SERVICE=orclXDB)'
[oracle@localhost ~]$ cd /oracle/oradata/orcl
[oracle@localhost orcl]$ ls
control01.ctl example01.dbf redo02.log sysaux01.dbf temp01.dbf users01.dbf control03.ctl redo01.log redo03.log system01.dbf undotbs01.dbf [oracle@localhost orcl]$ cp control01.ctl ./control04.ctl # 复制一份control file，命名为control04.ctl
SQL> startuppfile=$ORACLE_HOME/dbs/initorcl.ora
-- 指定PFILE来启动数据库 ORACLE instance started. Total System Global Area 422670336 bytes Fixed Size 1336960 bytes Variable Size 318769536 bytes Database Buffers 96468992 bytes Redo Buffers 6094848 bytes Database mounted. Database opened.
SQL> showparameter control
NAME TYPE VALUE ------------------------------------ ----------------------------------------------------------------------- control_file_record_keep_time integer 7 control_files string /oracle/oradata/orcl/control01 .ctl, /oracle/flash_recovery_a rea/orcl/control02.ctl,/oracl e/oradata/orcl/control03.ctl, /oracle/oradata/orcl/control04.ctl -- 可以看到又多了一个control file control_management_pack_access string DIAGNOSTIC+TUNING
3. 使用OMF来复用control file
使用OMF时，无需指定CONTROL_FILES这个参数，但是要指定DB_CREATE_ONLINE_LOG_DEST_n这个参数，启动数据库后，control file会创建在DB_CREATE_ONLINE_LOG_DEST_n这个参数指定的目录下。这样创建出来的control file名字是随机起的，通过查阅alertSID.log可以获取这个名字。目前主要以手动创建数据库为主，故不对OMF的使用详解。
四、管理ControlFile
有关control file的信息可以通过查询动态性能表V$CONTROLFILE,V$PARAMETER和V$CONTROLFILE_RECORD_SECTION获得，也可以使用SHOW PARAMETERCONTROL_FILES命令，建议使用SHOW PARAMETER CONTROL_FILES命令，可以避免输入错误，且支持通配符。
SQL> descv$controlfile;
Name Null? Type ------------------------------------------------- ---------------------------- STATUS VARCHAR2(7) NAME VARCHAR2(513) IS_RECOVERY_DEST_FILE VARCHAR2(3) BLOCK_SIZE NUMBER FILE_SIZE_BLKS NUMBER
SQL> select *from v$controlfile;
STATUS NAME IS_BLOCK_SIZE FILE_SIZE_BLKS --------------------------------------------------------- --------------------------------------------------------- /oracle/oradata/orcl/control01.ctl NO 16384 594 /oracle/flash_recovery_area/orcl/control02.ctl NO 16384 594 /oracle/oradata/orcl/control03.ctl NO 16384 594 /oracle/oradata/orcl/control04.ctl NO 16384 594
SQL> descv$controlfile_record_section;
Name Null? Type ------------------------------------------------- ---------------------------- TYPE VARCHAR2(28) RECORD_SIZE NUMBER RECORDS_TOTAL NUMBER RECORDS_USED NUMBER FIRST_INDEX NUMBER LAST_INDEX NUMBER LAST_RECID NUMBER
SQL> selecttype, records_total, records_used from v$controlfile_record_section;
TYPE RECORDS_TOTALRECORDS_USED ------------------------------------------------------------------------------------------------ DATABASE 1 1 CKPT PROGRESS 11 0 REDO THREAD 8 1 REDO LOG 16 3 DATAFILE 100 5 FILENAME 2298 9 ... ACM OPERATION 64 6 FOREIGN ARCHIVED LOG 1002 0 37 rows selected.
上表中列出的type的具体含义，可以通过查询联机文档Reference中的v$controlfile_record_section获得
五、Control File遗失情况演示
=======将controlfile移走========
[oracle@localhost dbs]$ cd /oracle/oradata/orcl
[oracle@localhost orcl]$ ls
control01.ctl control04.ctl redo01.log redo03.log system01.dbf undotbs01.dbf control03.ctl example01.dbf redo02.log sysaux01.dbf temp01.dbf users01.dbf
[oracle@localhost orcl]$ mkdir old
[oracle@localhost orcl]$ mv control0* old/
[oracle@localhost orcl]$ cd /oracle/flash_recovery_area/orcl/
[oracle@localhost orcl]$ ls
control02.ctl
[oracle@localhost orcl]$ mkdir backup
[oracle@localhost orcl]$ mv control02.ctl backup/
========启动数据库========
SQL> startup
ORACLE instance started. Total System Global Area 422670336 bytes Fixed Size 1336960 bytes Variable Size 318769536 bytes Database Buffers 96468992 bytes Redo Buffers 6094848 bytes ORA-00205: error in identifying control file, check alertlog for more info -- 报错了，提示无法确认control file
=======查看alertSID.log=======
[oracle@localhost ~]$ cd /oracle/diag/rdbms/orcl/orcl/trace
[oracle@localhost trace]$ vim alert_orcl.log
Wed Sep 10 00:43:12 2014 ALTER DATABASE MOUNT ORA-00210: cannot open the specified control file ORA-00202: control file:'/oracle/oradata/orcl/control03.ctl' ORA-27037: unable to obtain file status Linux Error: 2: No such file or directory Additional information: 3 ORA-00210: cannot open the specified control file ORA-00202: control file:'/oracle/flash_recovery_area/orcl/control02.ctl' ORA-27037: unable to obtain file status Linux Error: 2: No such file or directory Additional information: 3 ORA-00210: cannot open the specified control file ORA-00202: control file: '/oracle/oradata/orcl/control01.ctl' ORA-27037: unable to obtain file status Linux Error: 2: No such file or directory
========关闭数据库=======
SQL> shutdown immediate
ORA-01507: database not mounted ORACLE instance shut down.
=========把controlfile 还原========
[oracle@localhost ~]$ cd /oracle/flash_recovery_area/orcl/
[oracle@localhost orcl]$ mv backup/control02.ctl ./
[oracle@localhost orcl]$ cd /oracle/oradata/orcl
[oracle@localhost orcl]$ mv old/control0* ./
===========再次启动数据库=========
SQL> startup
ORACLE instance started. Total System Global Area 422670336 bytes Fixed Size 1336960 bytes Variable Size 318769536 bytes Database Buffers 96468992 bytes Redo Buffers 6094848 bytes Database mounted. Database opened. -- 能够成功启动数据库了