CREATE CONTROLFILE

Purpose

Use the CREATE CONTROLFILE statement to re-create a control file in one of the following cases:

• All copies of your existing control files have been lost through media failure.
• You want to change the name of the database.
• You want to change the maximum number of redo log file groups, redo log file members, archived redo log files, datafiles, or instances that can concurrently have the database mounted and open.

  Note: If it is necessary to use the CREATE CONTROLFILE statement, do not include in the DATAFILE clause any datafiles in temporary or read-only tablespaces. You can add these types of files to the database later. An alternative to the CREATE CONTROLFILE statement is ALTER DATABASE BACKUP CONTROLFILE TO TRACE, which generates a SQL script in the trace file to re-create the controlfile. If your database contains any read-only or temporary tablespaces, that SQL script will also contain all the necessary SQL statements to add those files back into the database.

  See Also: "BACKUP CONTROLFILE Clause" of ALTER DATABASE for information creating a script based on an existing database controlfile

When you issue a CREATE CONTROLFILE statement, Oracle creates a new control file based on the information you specify in the statement. If you omit any clauses, Oracle uses the default values rather than the values for the previous control file. After successfully creating the control file, Oracle mounts the database in the mode specified by the initialization parameter CLUSTER_DATABASE. You then must perform media recovery before opening the database. It is recommended that you then shut down the instance and take a full backup of all files in the database.

Prerequisites

To create a control file, you must have the SYSDBA system privilege.

The database must not be mounted by any instance. Oracle leaves the database mounted in EXCLUSIVE state after successful creation of the control file. If you are using Oracle with Real Application Clusters, the DBA must then shut down and remount the database in SHARED mode (which is the default if the value of the CLUSTER_DATABASE initialization parameter is TRUE) before other instances can start up.

If the REMOTE_LOGIN_PASSWORDFILE initialization parameter is set to EXCLUSIVE, Oracle returns an error when you attempt to re-create the control file. To avoid this message, either set the parameter to SHARED, or re-create your password file before re-creating the control file.

Syntax

create_controlfile::=

Text description of create_controlfile

(datafile_tempfile_spec::=--part of file_specification syntax)

logfile_clause::=

Text description of logfile_clause

(redo_log_file_spec::=--part of file_specification syntax)

character_set_clause::=

Text description of character_set_clause

Semantics

REUSE

Specify REUSE to indicate that existing control files identified by the initialization parameter CONTROL_FILES can be reused, thus ignoring and overwriting any information they may currently contain. If you omit this clause and any of these control files already exists, Oracle returns an error.

DATABASE Clause

Specify the name of the database. The value of this parameter must be the existing database name established by the previous CREATE DATABASE statement or CREATE CONTROLFILE statement.

SET DATABASE Clause

Use SET DATABASE to change the name of the database. The name of a database can be as long as eight bytes.

logfile_clause

Use the logfile_clause to specify the redo log files for your database. You must list all members of all redo log file groups.

GROUP integer

Specify the logfile group number. If you specify GROUP values, Oracle verifies these values with the GROUP values when the database was last open.

If you omit this clause, Oracle creates logfiles using system default values. In addition, if either the DB_CREATE_ONLINE_LOG_DEST_n or DB_CREATE_FILE_DEST initialization parameter (or both) has been set, and if you have specified RESETLOGS, then Oracle creates two logs in the default logfile destination specified in the DB_CREATE_ONLINE_LOG_DEST_n parameter, and if it is not set, then in the DB_CREATE_FILE_DEST parameter.

RESETLOGS

Specify RESETLOGS if you want Oracle to ignore the contents of the files listed in the LOGFILE clause. These files do not have to exist. Each redo_log_file_spec in the LOGFILE clause must specify the SIZE parameter. Oracle assigns all online redo log file groups to thread 1 and enables this thread for public use by any instance. After using this clause, you must open the database using the RESETLOGS clause of the ALTER DATABASE statement.

NORESETLOGS

Specify NORESETLOGS if you want Oracle to use all files in the LOGFILE clause as they were when the database was last open. These files must exist and must be the current online redo log files rather than restored backups. Oracle reassigns the redo log file groups to the threads to which they were previously assigned and reenables the threads as they were previously enabled.

DATAFILE Clause

Specify the datafiles of the database. You must list all datafiles. These files must all exist, although they may be restored backups that require media recovery. See the syntax description in file_specification.

Restriction on DATAFILE

You cannot specify the autoextend_clause of data_file_spec in this DATAFILE clause.

MAXLOGFILES Clause

Specify the maximum number of online redo log file groups that can ever be created for the database. Oracle uses this value to determine how much space in the control file to allocate for the names of redo log files. The default and maximum values depend on your operating system. The value that you specify should not be less than the greatest GROUP value for any redo log file group.

MAXLOGMEMBERS Clause

Specify the maximum number of members, or identical copies, for a redo log file group. Oracle uses this value to determine how much space in the control file to allocate for the names of redo log files. The minimum value is 1. The maximum and default values depend on your operating system.

MAXLOGHISTORY Clause

This parameter is useful only if you are using Oracle in ARCHIVELOG mode with Real Application Clusters. Specify the maximum number of archived redo log file groups for automatic media recovery of Real Application Clusters. Oracle uses this value to determine how much space in the control file to allocate for the names of archived redo log files. The minimum value is 0. The default value is a multiple of the MAXINSTANCES value and depends on your operating system. The maximum value is limited only by the maximum size of the control file.

MAXDATAFILES Clause

Specify the initial sizing of the datafiles section of the control file at CREATE DATABASE or CREATE CONTROLFILE time. An attempt to add a file whose number is greater than MAXDATAFILES, but less than or equal to DB_FILES, causes the control file to expand automatically so that the datafiles section can accommodate more files.

The number of datafiles accessible to your instance is also limited by the initialization parameter DB_FILES.

MAXINSTANCES Clause

Specify the maximum number of instances that can simultaneously have the database mounted and open. This value takes precedence over the value of the initialization parameter INSTANCES. The minimum value is 1. The maximum and default values depend on your operating system.

ARCHIVELOG | NOARCHIVELOG

Specify ARCHIVELOG to archive the contents of redo log files before reusing them. This clause prepares for the possibility of media recovery as well as instance or system failure recovery.

If you omit both the ARCHIVELOG clause and NOARCHIVELOG clause, Oracle chooses NOARCHIVELOG mode by default. After creating the control file, you can change between ARCHIVELOG mode and NOARCHIVELOG mode with the ALTER DATABASE statement.

FORCE LOGGING

Use this clause to put the database into FORCE LOGGING mode after control file creation. When the database is in this mode, Oracle logs all changes in the database except changes to temporary tablespaces and temporary segments. This setting takes precedence over and is independent of any NOLOGGING or FORCE LOGGING settings you specify for individual tablespaces and any NOLOGGING settings you specify for individual database objects. If you omit this clause, the database will not be in FORCE LOGGING mode after the controlfile is created.

character_set_clause

If you specify a character set, Oracle reconstructs character set information in the control file. In case media recovery of the database is required, this information will be available before the database is open, so that tablespace names can be correctly interpreted during recovery. This clause is required only if you are using a character set other than the default US7ASCII. Oracle prints the current database character set to the "alert" log in $ORACLE_HOME/log during startup.

If you are re-creating your control file and you are using Recovery Manager for tablespace recovery, and if you specify a different character set from the one stored in the data dictionary, then tablespace recovery will not succeed. (However, at database open, the control file character set will be updated with the correct character set from the data dictionary.)

Example

Creating a Controlfile: Example

This statement re-creates a control file. In this statement, database demo was created with the WE8DEC character set. The example uses the word path where you would normally insert the path on your system to the appropriate Oracle directories.

STARTUP NOMOUNT

CREATE CONTROLFILE REUSE DATABASE "demo" NORESETLOGS NOARCHIVELOG
    MAXLOGFILES 32
    MAXLOGMEMBERS 2
    MAXDATAFILES 32
    MAXINSTANCES 1
    MAXLOGHISTORY 449
LOGFILE
  GROUP 1 '/path/oracle/dbs/t_log1.f'  SIZE 500K,
  GROUP 2 '/path/oracle/dbs/t_log2.f'  SIZE 500K
# STANDBY LOGFILE
DATAFILE
  '/path/oracle/dbs/t_db1.f',
  '/path/oracle/dbs/dbu19i.dbf',
  '/path/oracle/dbs/tbs_11.f',
  '/path/oracle/dbs/smundo.dbf',
  '/path/oracle/dbs/demo.dbf'
CHARACTER SET WE8DEC
;