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In Oracle, the control file is the file used when the database is mounted. If the control file is lost or damaged, the instance will crash, and the parameter file records the location of the control file.

After the instance is launched to nomount, you can only mount if the db_names parameter is the same as the database name recorded in the control file, otherwise an error will be reported

To launch the instance to mount, it will determine the location and number of control files as well as the consistency

The control file records the structure and behavior of the database instance, including database data file, redo log file, database name, database creation information, tablespace information, data file status, log file information, backup information, checkpoint information, etc.

A database must have at least one control file, a maximum of 8, generally set to 2, under different paths.

When managing control files, DBA needs to pay attention to:

1. Control the number of files

2. Control file version problem

3. Control file backup (cold backup, hot backup)

4. Control the file size within 100m.

The following is the view related to the control file in Oracle:

V$DATABASE records the database information read in the control file

V$CONTROLFILE record control file details

V$CONTROLFILE_RECORD_SECTIONG record controls the contents of the file record

V$PARAMETER records the control file parameters corresponding to the CONTROL_FILES parameter

For example, we can look at the location of the control file in V$CONTROLFILE:

SQL > select name from v$controlfile

NAME

/ u01/oracle/oradata/wyzc/control01.ctl

/ data1/oracle/oradata/control02.ctl

/ data2/oracle/oradata/control03.ctl

If we want to know what information is recorded in the control file, we can use V$CONTROLFILE_RECORD_SECTIONG

SQL > select type from v$controlfile_record_section

TYPE

-

DATABASE

CKPT PROGRESS

REDO THREAD

REDO LOG

DATAFILE

FILENAME

TABLESPACE

TEMPORARY FILENAME

RMAN CONFIGURATION

LOG HISTORY

OFFLINE RANGE

ARCHIVED LOG

BACKUP SET

BACKUP PIECE

BACKUP DATAFILE

BACKUP REDOLOG

DATAFILE COPY

BACKUP CORRUPTION

COPY CORRUPTION

DELETED OBJECT

PROXY COPY

BACKUP SPFILE

DATABASE INCARNATION

FLASHBACK LOG

RECOVERY DESTINATION

INSTANCE SPACE RESERVATION

REMOVABLE RECOVERY FILES

RMAN STATUS

THREAD INSTANCE NAME MAPPING

MTTR

DATAFILE HISTORY

STANDBY DATABASE MATRIX

GUARANTEED RESTORE POINT

RESTORE POINT

DATABASE BLOCK CORRUPTION

ACM OPERATION

FOREIGN ARCHIVED LOG

37 rows selected.

In the Oracle 11g R2 version, a total of 37 contents were recorded in the control file, as above.

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