Control files are used to record and maintain databases. When the database is restored, the server process and background process need to read various backup-related information from the control file. If the control file is corrupted, the backup information will be lost. Although the use of diverse control files can prevent Control File Corruption, control files should be backed up on a regular basis due to the importance of control files. When the database configuration changes, you must back up the control file. Commands that involve database configuration changes:
Alter database [add | drop] logfile
Alter database [add | drop] logfile member
Alter database [add | drop] logfile group
Alter database [noarchivelog | archivelog]
Alter database rename file
Create tablespace
Alter tablespace [add | rename] datafile
Alter tablespace [read write | read only]
Drop tablespace
Control file backup in three ways
1) Use the OS command to copy
1) Use the alter database command to generate a control file copy in the open state.
2) In the open state, use the alter database backup controlfile to trace command to back up the control file to the trace file
Two methods are available to control file recovery.
1) Use recover database using backup controlfile in the mount status
2) in the mount status, the trace file is generated and restored.
2-2 example:
[Oracle @ localhost ~] $ Rlsqlplus/as sysdba
SQL * Plus: Release 10.2.0.1.0-Production on Monday August 1 21:40:03 2011
Copyright (c) 1982,200 5, Oracle. All rights reserved.
Connected to an idle instance.
SQL> startup
ORACLE instance started.
Total System Global Area 528482304 bytes
Fixed Size 1220360 bytes
Variable Size 176161016 bytes
Database Buffers 343932928 bytes
Redo Buffers 7168000 bytes
Database mounted.
Database opened.
-- Generate a control file copy in the open state
SQL> alter database backup controlfile
2'/oracle/10g/oracle/bakup/database/oralife. ctl ';
Alter database backup controlfile
*
ERROR at line 1:
ORA-01580: error creating control backup file
/Oracle/10g/oracle/bakup/database/oralife. ctl
ORA-27038: created file already exists
Additional information: 1
SQL> alter database backup controlfile
2 '/oracle/10g/oracle/bakup/database/oralife. ctl' reuse; -- Reuse is used to overwrite the original control file copy.
Database altered.
-- Manually delete all control file simulated file loss
SQL> ho rm/oracle/10g/oracle/product/10.2.0/oradata/oralife/*. ctl;
-- Use evan to log on and add data
SQL> conn evan/evan
Connected.
SQL> select * from t_evan;
TEXT
--------------------------------------------------------------------------------
Oracle
Java
Spring
Hibernate
Hibernate
SQL> insert into t_evan values ('added ');
1 row created.
SQL> commit;
Commit complete.
SQL> conn/as sysdba
Connected.
SQL> shutdown immediate
ORA-00210: cannot open the specified control file
ORA-00202: control file: '/oracle/10g/oracle/product/10.2.0/oradata/oralife/control01.ctl'
ORA-27041: unable to open file
Linux Error: 2: No such file or directory
Additional information: 3
SQL> shutdown abort
ORACLE instance shut down.
-- Alter_oralife.log:
Mon Aug 1 23:13:51 2011
ORA-00202: control file: '/oracle/10g/oracle/product/10.2.0/oradata/oralife/control01.ctl'
ORA-27037: unable to obtain file status
Linux Error: 2: No such file or directory
Additional information: 3
-- Copy the control file to the target path
SQL> ho cp/oracle/10g/oracle/bakup/database/oralife. ctl/oracle/10g/oracle/product/10.2.0/oradata/oralife/control01.ctl
SQL> alter system set control_files = '/oracle/10g/oracle/product/10.2.0/oradata/oralife/control01.ctl' scope = spfile; -- Modify the control_files parameter to specify available control files
System altered.
SQL> startup force mount
ORACLE instance started.
Total System Global Area 528482304 bytes
Fixed Size 1220360 bytes
Variable Size 138412280 bytes
Database Buffers 381681664 bytes
Redo Buffers 7168000 bytes
Database mounted.
-- Generate a trace file
SQL> alter database backup controlfile to trace noresetlogs;
Database altered.
SELECT c. VALUE | '/' | d. instance_name | '_ ora _' | a. spid | '. trc' TRACE
FROM v $ process a, v $ session B, v $ parameter c, v $ instance d
WHERE a. addr = B. paddr
AND B. audsid = USERENV ('sessionid ')
AND c. NAME = 'user _ dump_dest ';
TRACE
--------------------------------------------------------------------------------
/Oracle/10g/oracle/product/10.2.0/db_1/admin/oralife/udump/oralife_ora_4558.trc
SQL> shutdown immediate
ORA-01109: database not open
Database dismounted.
ORACLE instance shut down.
-- Open the trace file, remove comments, execute the script in the shutdown state, and create the control file.
-- Use evan to log on and verify the data
SQL> conn evan/evan
Connected.
SQL> select * from t_evan;
TEXT
--------------------------------------------------------------------------------
Oracle
Java
Spring
Hibernate
Hibernate
Added
6 rows selected.
The data is not lost.
SQL> select name from v $ controlfile;
NAME
--------------------------------------------------------------------------------
/Oracle/10g/oracle/product/10.2.0/oradata/oralife/control01.ctl
Then Multiple control files should be rebuilt.
How to do it?
