1月11日
CREATE CONTROLFILE
CREATE CONTROLFILE command
PURPOSE:
To recreate a control file in one of these 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 logfile groups, redo log file members, archived redo log files, data files, or instances that can concurrently have the database mounted and open.
Warning: Oracle Corporation recommends that you perform a full backup of all files in the database before using this command.
SYNTAX:
CREATE CONTROLFILE [REUSE]
[SET] DATABASE database
LOGFILE [GROUP int] filespec [,[GROUP int] filespec]...
{RESETLOGS | NORESETLOGS}
DATAFILE filespec [, filespec] ...
[MAXLOGFILES integer]
[MAXLOGMEMBERS integer]
[MAXLOGHISTORY integer]
[MAXDATAFILES integer]
[MAXINSTANCES integer]
[ARCHIVELOG | NOARCHIVELOG]
where:
REUSE specifies that existing control files identified by the initialization parameter CONTROL_FILES can be reused, thus ignoring and overwriting any and all information they may currently contain. If you omit this option and any of these control files already exist, Oracle 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. These files must all exist.
RESETLOGS ignores the contents of the files listed in the LOGFILE clause. Each filespec in the LOGFILE clause must specify the SIZE parameter. Oracle 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 be the current redo log files rather than restored backups. Oracle 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, Oracle 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.
MAXLOGFILES specifies the maximum number of 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.
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. 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 specifies the maximum number of archived redo log file groups for automatic media recovery of the Oracle Parallel Server. 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 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 Oracle 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, Oracle chooses noarchivelog mode by default. After creating the control file, you can change between archivelog mode and noarchivelog mode with the ALTER DATABASE command.
PREREQUISITES: You must have the OSDBA role enabled. The database must not be mounted by any instance.
If you are using Trusted Oracle in DBMS MAC mode, your operating system label must be the equivalent of DBHIGH.
