Oracle Control File Contents

An Oracle control file contains information about the associated database that is required for access by an instance, both at startup and during normal operation. Control file information can be modified only by Oracle; no database administrator or user can edit a control file.

Among other things, a control file contains information such as:

■ The database name

■ The timestamp of database creation

■ The names and locations of associated datafiles and redo log files

■ Tablespace information

■ Datafile offline ranges

■ The log history

■ Archived log information

■ Backup set and backup piece information

■ Backup datafile and redo log information

■ Datafile copy information

■ The current log sequence number

■ Checkpoint information

The database name and timestamp originate at database creation. The database name is taken from either the name specified by the DB_NAME initialization parameter or the name used in the CREATE DATABASE statement.

Each time that a datafile or a redo log file is added to, renamed in, or dropped from the database, the control file is updated to reflect this physical structure change. These changes are recorded so that:

■ Oracle can identify the datafiles and redo log files to open during database startup

■ Oracle can identify files that are required or available in case database recovery is necessary

Therefore, if you make a change to the physical structure of your database (using ALTER DATABASE statements), then you should immediately make a backup of your control file.

Control files also record information about checkpoints. Every three seconds, the checkpoint process (CKPT) records information in the control file about the checkpoint position in the redo log. This information is used during database recovery to tell Oracle that all redo entries recorded before this point in the redo log group are not necessary for database recovery; they were already written to the datafiles.

V$CONTROLFILE displays the names of the control files.

select * from V$CONTROLFILE;

STATUS	NAME	IS_RECOVERY_DEST_FILE	BLOCK_SIZE	FILE_SIZE_BLKS
	/fs/u03/oracle_data/mydb/control01.ctl	NO	16384	2886
	/fs/u03/oracle_data/ mydb/control02.ctl	NO	16384	2886
	/fs/u03/oracle_data/ mydb/control03.ctl	NO	16384	2886

V$CONTROLFILE_RECORD_SECTION displays information about the control file record sections.

select * from V$CONTROLFILE_RECORD_SECTION;

TYPE	RECORD_ SIZE	RECORDS_ TOTAL	RECORDS_ USED	FIRST_ INDEX	LAST_ INDEX	LAST_ RECID
DATABASE	316	1	1	0	0	0
CKPT PROGRESS	8180	4	0	0	0	0
REDO THREAD	256	1	1	0	0	0
REDO LOG	72	20	15	0	0	128
DATAFILE	428	798	512	0	0	2166
FILENAME	524	2809	554	0	0	0
TABLESPACE	68	300	124	0	0	159
TEMPORARY FILENAME	56	300	38	0	0	95
RMAN CONFIGURATION	1108	50	2	0	0	6
LOG HISTORY	56	20450	20450	5005	5004	376730
OFFLINE RANGE	200	584	0	0	0	0
ARCHIVED LOG	584	20309	20309	17993	17992	376739
BACKUP SET	40	4090	4090	3525	3524	192073
BACKUP PIECE	736	3734	3734	627	626	192073
BACKUP DATAFILE	116	5076	5076	3352	3351	275904
BACKUP REDOLOG	76	14636	14636	11204	11203	329751
DATAFILE COPY	660	619	260	1	260	260
BACKUP CORRUPTION	44	371	0	0	0	0
COPY CORRUPTION	40	409	0	0	0	0
DELETED OBJECT	20	65535	65535	9906	9905	794594
PROXY COPY	852	652	0	0	0	0
BACKUP SPFILE	36	454	136	1	136	136
DATABASE INCARNATION	56	292	1	1	1	1
FLASHBACK LOG	84	2048	0	0	0	0
RECOVERY DESTINATION	180	1	0	0	0	0
INSTANCE SPACE RESERVATION	28	1055	1	0	0	0
REMOVABLE RECOVERY FILES	32	1000	0	0	0	0
RMAN STATUS	116	1128	1128	538	537	17880
THREAD INSTANCE NAME MAPPING	80	1	1	0	0	0
MTTR	100	1	1	0	0	0
DATAFILE HISTORY	568	57	0	0	0	0
STANDBY DATABASE MATRIX	400	10	10	0	0	0
GUARANTEED RESTORE POINT	212	2048	0	0	0	0
RESTORE POINT	212	2083	0	0	0	0

Oracle dynamic performance views