Oracle7 Server SQL Reference

CREATE CONTROLFILE

Purpose

To recreate 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, data files, or instances that can concurrently have the database mounted and open.

Warning: It is recommended that you perform a full backup of all files in the database before using this command.

Prerequisites

You must have the OSDBA role enabled. The database must not be mounted by any instance.

If you are using Trusted Oracle7 in DBMS MAC mode, your operating system label must be the equivalent of DBHIGH.

Syntax

Keywords and Parameters

REUSE

specifies 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 option and any of these control files already exist, Oracle7 returns an error.

SET DATABASE

changes the name of the database. The name of a database can be as long as eight bytes.

DATABASE

specifies 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.

LOGFILE

specifies the redo log file groups for your database. You must list all members of all redo log file groups. See the syntax description of filespec .

RESETLOGS

ignores the contents of the files listed in the LOGFILE clause. These files do not have to exist. Each filespec in the LOGFILE clause must specify the SIZE parameter. Oracle7 assigns all redo log file groups to thread 1 and enables this thread for public use by any instance. After using this option, you must open the database using the RESETLOGS option of the ALTER DATABASE command.

NORESETLOGS

specifies that all files in the LOGFILE clause should be used as they were when the database was last open. These files must exit and must be the current redo log files rather than restored backups. Oracle7 reassigns the redo log file groups to the threads to which they were previously assigned and re-enables the threads as they were previously enabled. If you specify GROUP values, Oracle7 verifies these values with the GROUP values when the database was last open.

DATAFILE

specifies the data files of the database. You must list all data files. These files must all exist, although they may be restored backups that require media recovery. See the syntax description of filespec .

MAXLOGFILES

specifies the maximum number of redo log file groups that can ever be created for the database. Oracle7 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.

Note that the number of redo log file groups accessible to your instance is also limited by the initialization parameter LOG_FILES.

MAXLOGMEMBERS

specifies the maximum number of members, or copies, for a redo log file group. Oracle7 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

specifies the maximum number of archived redo log file groups for automatic media recovery of the Oracle7 Parallel Server. Oracle7 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 varies depending on your operating system. The maximum value is limited only by the maximum size of the control file. Note that this parameter is only useful if you are using Oracle7 with the Parallel Server option in both parallel mode and archivelog mode.

MAXDATAFILES

specifies the maximum number of data files that can ever be created for the database. The minimum value is 1. The maximum and default values depend on your operating system. The value you specify should not be less than the total number of data files ever in the database, including those for tablespaces that have been dropped.

Note that the number of data files accessible to your instance is also limited by the initialization parameter DB_FILES.

MAXINSTANCES

specifies 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

establishes the mode of archiving the contents of redo log files before reusing them. This option prepares for the possibility of media recovery as well as instance recovery.

NOARCHIVELOG

establishes the initial mode of reusing redo log files without archiving their contents. This option prepares for the possibility of instance recovery but not media recovery.

If you omit both the ARCHIVELOG and NOARCHIVELOG options, Oracle7 chooses noarchivelog mode by default. After creating the control file, you can change between archivelog mode and noarchivelog mode with the ALTER DATABASE command.

Usage Notes

It is recommended that you take a full backup of all files in the database before issuing a CREATE CONTROLFILE statement.

When you issue a CREATE CONTROLFILE statement, Oracle7 creates a new control file based on the information you specify in the statement. If you omit any of the options from the statement, Oracle7 uses the default options, rather than the options for the previous control file. After successfully creating the control file, Oracle7 mounts the database in exclusive mode. You then must perform media recovery before opening the database. It is recommended that you then shutdown the instance and take a full backup of all files in the database.

For more information on using this command, see the "Recovering a Database" chapter of Oracle7 Server Administrator's Guide.

When you create a control file in Trusted Oracle7, it is labeled with your DBMS label. The control file cannot be used unless it is labeled at the operating system equivalent of DBHIGH. If you issue a CREATE CONTROLFILE statement in DBMS MAC mode, Trusted Oracle7 automatically switches to OS MAC mode. You can then return to DBMS MAC mode by issuing an ALTER DATABASE statement with the SET DBMAC ON clause.

Example

This example recreates a control file:

CREATE CONTROLFILE REUSE

	SET DATABASE orders_2

	LOGFILE GROUP 1 ('diskb:log1.log', 'diskc:log1.log') SIZE 50K,

	        GROUP 2 ('diskb:log2.log', 'diskc:log2.log') SIZE 50K

	NORESETLOGS

	DATAFILE 'diska:dbone.dat' SIZE 2M

	MAXLOGFILES 5

	MAXLOGHISTORY 100

	MAXDATAFILES 10

	MAXINSTANCES 2