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控制文件（Control File）是 Oracle 的物理文件之一，它记录了数据库的名字、数据文件的位置等信息。控制文件的重要性在于，一旦控制文件损坏，数据库将会宕机。控制文件是一个很小的二进制文件，用户不能编辑控制文件，控制文件的修改由 Oracle 自动完成。那么，我们能够查看控制文件里面的具体信息吗？答案是可以的，我们可以通过转储文件来获得控制文件的详细信息。
1. 生成控制文件的转储文件
SQL> select * from v$version;
BANNER
——————————————————————————–
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 – Production
PL/SQL Release 11.2.0.3.0 – Production
CORE 11.2.0.3.0 Production
TNS for Linux: Version 11.2.0.3.0 – Production
NLSRTL Version 11.2.0.3.0 – Production
SQL> alter database backup controlfile to trace ;
Database altered.
SQL>
2. 查找生成的转储文件
我们知道，用户生成的 TRACE 文件存储在 udump 目录下。在 Oracle10g 中，udump 路径是 $ORACLE_HOME/admin/SID/udump，而 Oracle11g 则大不一样。我们可以通过查看 user_dump_dest 参数来定位 udump 目录的具体位置。
SQL> show parameter user_dump_dest
NAME TYPE VALUE
———————————— ———– ——————————
user_dump_dest string /u01/app/oracle/diag/rdbms/linuxidc/HOEGH/trace
SQL>
然后，我们使用 ls 命令找到最近生成的 TRACE 文件，就是图示的 linuxidc_ora_304.trc 文件。
[oracle@linuxidc trace]$ ls -ltr
total 1332
此处省略三百字
-rw-r—– 1 oracle oinstall 932 May 9 21:26 linuxidc_mmon_4805.trm
-rw-r—– 1 oracle oinstall 9750 May 9 21:26 linuxidc_mmon_4805.trc
-rw-r—– 1 oracle oinstall 4562 May 9 21:28 linuxidc_dbrm_4789.trm
-rw-r—– 1 oracle oinstall 80534 May 9 21:28 linuxidc_dbrm_4789.trc
-rw-r—– 1 oracle oinstall 97 May 9 21:29 linuxidc_ora_304.trm
-rw-r—– 1 oracle oinstall 12786 May 9 21:29 linuxidc_ora_304.trc
3. 查看控制文件具体信息
现在，我们就可以通过 more 命令来查看控制文件的具体信息了。
[oracle@linuxidc trace]$ more linuxidc_ora_304.trc
Trace file /u01/app/oracle/diag/rdbms/linuxidc/HOEGH/trace/linuxidc_ora_304.trc
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 – Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
ORACLE_HOME = /u01/app/oracle/product/11.2.0/dbhome_1
System name: Linux
Node name: linuxidc.example.com
Release: 2.6.18-164.el5PAE
Version: #1 SMP Thu Sep 3 02:28:20 EDT 2009
Machine: i686
VM name: VMWare Version: 6
Instance name: linuxidc
Redo thread mounted by this instance: 1
Oracle process number: 26
Unix process pid: 304, image: oracle@linuxidc.example.com (TNS V1-V3)
*** 2016-05-09 21:29:07.246
— The following are current System-scope REDO Log Archival related
— parameters and can be included in the database initialization file.
—
— LOG_ARCHIVE_DEST=”
— LOG_ARCHIVE_DUPLEX_DEST=”
—
— LOG_ARCHIVE_FORMAT=%t_%s_%r.dbf
—
— DB_UNIQUE_NAME=”linuxidc”
—
— LOG_ARCHIVE_CONFIG=’SEND, RECEIVE, NODG_CONFIG’
— LOG_ARCHIVE_MAX_PROCESSES=4
— STANDBY_FILE_MANAGEMENT=MANUAL
— STANDBY_ARCHIVE_DEST=?/dbs/arch
— FAL_CLIENT=”
— FAL_SERVER=”
—
— LOG_ARCHIVE_DEST_1=’LOCATION=/u01/app/oracle/product/11.2.0/dbhome_1/dbs/arch
‘
— LOG_ARCHIVE_DEST_1=’MANDATORY NOREOPEN NODELAY’
— LOG_ARCHIVE_DEST_1=’ARCH NOAFFIRM EXPEDITE NOVERIFY SYNC’
— LOG_ARCHIVE_DEST_1=’NOREGISTER NOALTERNATE NODEPENDENCY’
— LOG_ARCHIVE_DEST_1=’NOMAX_FAILURE NOQUOTA_SIZE NOQUOTA_USED NODB_UNIQUE_NAME’
— LOG_ARCHIVE_DEST_1=’VALID_FOR=(PRIMARY_ROLE,ONLINE_LOGFILES)’
— LOG_ARCHIVE_DEST_STATE_1=ENABLE
—
— Below are two sets of SQL statements, each of which creates a new
— control file and uses it to open the database. The first set opens
— the database with the NORESETLOGS option and should be used only if
— the current versions of all online logs are available. The second
— set opens the database with the RESETLOGS option and should be used
— if online logs are unavailable.
— The appropriate set of statements can be copied from the trace into
— a script file, edited as necessary, and executed when there is a
— need to re-create the control file.
—
— Set #1. NORESETLOGS case
—
— The following commands will create a new control file and use it
— to open the database.
— Data used by Recovery Manager will be lost.
— Additional logs may be required for media recovery of offline
— Use this only if the current versions of all online logs are
— available.
— After mounting the created controlfile, the following SQL
— statement will place the database in the appropriate
— protection mode:
— ALTER DATABASE SET STANDBY DATABASE TO MAXIMIZE PERFORMANCE
STARTUP NOMOUNT
CREATE CONTROLFILE REUSE DATABASE “linuxidc” NORESETLOGS NOARCHIVELOG
MAXLOGFILES 16
MAXLOGMEMBERS 3
MAXDATAFILES 100
MAXINSTANCES 8
MAXLOGHISTORY 292
LOGFILE
GROUP 1 ‘/u01/app/oracle/oradata/linuxidc/redo01.log’ SIZE 50M BLOCKSIZE 512,
GROUP 2 ‘/u01/app/oracle/oradata/linuxidc/redo02.log’ SIZE 50M BLOCKSIZE 512,
GROUP 3 ‘/u01/app/oracle/oradata/linuxidc/redo03.log’ SIZE 50M BLOCKSIZE 512
— STANDBY LOGFILE
DATAFILE
‘/u01/app/oracle/oradata/linuxidc/system01.dbf’,
‘/u01/app/oracle/oradata/linuxidc/sysaux01.dbf’,
‘/u01/app/oracle/oradata/linuxidc/undotbs01.dbf’,
‘/u01/app/oracle/oradata/linuxidc/users01.dbf’,
‘/u01/app/oracle/oradata/linuxidc/example01.dbf’,
‘/u01/app/oracle/oradata/linuxidc/test01.dbf’
CHARACTER SET AL32UTF8
;
— Commands to re-create incarnation table
— Below log names MUST be changed to existing filenames on
— disk. Any one log file from each branch can be used to
— re-create incarnation records.
— ALTER DATABASE REGISTER LOGFILE ‘/u01/app/oracle/product/11.2.0/dbhome_1/dbs/
arch1_1_762197622.dbf’;
— ALTER DATABASE REGISTER LOGFILE ‘/u01/app/oracle/product/11.2.0/dbhome_1/dbs/
arch1_1_860888149.dbf’;
— Recovery is required if any of the datafiles are restored backups,
— or if the last shutdown was not normal or immediate.
RECOVER DATABASE
— Database can now be opened normally.
ALTER DATABASE OPEN;
— Commands to add tempfiles to temporary tablespaces.
— Online tempfiles have complete space information.
— Other tempfiles may require adjustment.
ALTER TABLESPACE TEMP ADD TEMPFILE ‘/u01/app/oracle/oradata/linuxidc/temp01.dbf’
SIZE 30408704 REUSE AUTOEXTEND ON NEXT 655360 MAXSIZE 32767M;
— End of tempfile additions.
—
— Set #2. RESETLOGS case
—
— The following commands will create a new control file and use it
— to open the database.
— Data used by Recovery Manager will be lost.
— The contents of online logs will be lost and all backups will
— be invalidated. Use this only if online logs are damaged.
— After mounting the created controlfile, the following SQL
— statement will place the database in the appropriate
— protection mode:
— ALTER DATABASE SET STANDBY DATABASE TO MAXIMIZE PERFORMANCE
STARTUP NOMOUNT
CREATE CONTROLFILE REUSE DATABASE “linuxidc” RESETLOGS NOARCHIVELOG
MAXLOGFILES 16
MAXLOGMEMBERS 3
MAXDATAFILES 100
MAXINSTANCES 8
MAXLOGHISTORY 292
LOGFILE
GROUP 1 ‘/u01/app/oracle/oradata/linuxidc/redo01.log’ SIZE 50M BLOCKSIZE 512,
GROUP 2 ‘/u01/app/oracle/oradata/linuxidc/redo02.log’ SIZE 50M BLOCKSIZE 512,
GROUP 3 ‘/u01/app/oracle/oradata/linuxidc/redo03.log’ SIZE 50M BLOCKSIZE 512
— STANDBY LOGFILE
DATAFILE
‘/u01/app/oracle/oradata/linuxidc/system01.dbf’,
‘/u01/app/oracle/oradata/linuxidc/sysaux01.dbf’,
‘/u01/app/oracle/oradata/linuxidc/undotbs01.dbf’,
‘/u01/app/oracle/oradata/linuxidc/users01.dbf’,
‘/u01/app/oracle/oradata/linuxidc/example01.dbf’,
‘/u01/app/oracle/oradata/linuxidc/test01.dbf’
CHARACTER SET AL32UTF8
;
— Commands to re-create incarnation table
— Below log names MUST be changed to existing filenames on
— disk. Any one log file from each branch can be used to
— re-create incarnation records.
— ALTER DATABASE REGISTER LOGFILE ‘/u01/app/oracle/product/11.2.0/dbhome_1/dbs/
arch1_1_762197622.dbf’;
— ALTER DATABASE REGISTER LOGFILE ‘/u01/app/oracle/product/11.2.0/dbhome_1/dbs/
arch1_1_860888149.dbf’;
— Recovery is required if any of the datafiles are restored backups,
— or if the last shutdown was not normal or immediate.
RECOVER DATABASE USING BACKUP CONTROLFILE
— Database can now be opened zeroing the online logs.
ALTER DATABASE OPEN RESETLOGS;
— Commands to add tempfiles to temporary tablespaces.
— Online tempfiles have complete space information.
— Other tempfiles may require adjustment.
ALTER TABLESPACE TEMP ADD TEMPFILE ‘/u01/app/oracle/oradata/linuxidc/temp01.dbf
我们可以看到转储文件里包含了数据库的名字、数据文件的位置等信息，并且按照是否需要 resetlogs 分别给出了创建控制文件的 sql 语句。控制文件非常重要，我们可以把它备份下来以防万一。
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