| Oracle9i SQL Reference Release 2 (9.2) Part Number A96540-02 |
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| Oracle9i SQL Reference Release 2 (9.2) Part Number A96540-02 |
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View PDF |
Use the ALTER DATABASE statement to modify, maintain, or recover an existing database.
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You must have the ALTER DATABASE system privilege.
To specify the RECOVER clause, you must also have the SYSDBA system privilege.
alter_database::=
Groups of ALTER DATABASE syntax:
parallel_clause::=
recover_clause::=
cancel_clause::=
finish_clause::=
maxsize_clause::=
logfile_descriptor::=
trace_file_clause::=
commit_switchover_clause::=
Specify the name of the database to be altered. The database name can contain only ASCII characters. If you omit database, Oracle alters the database identified by the value of the initialization parameter DB_NAME. You can alter only the database whose control files are specified by the initialization parameter CONTROL_FILES. The database identifier is not related to the Oracle Net database specification.
The startup_clauses let you mount and open the database so that it is accessible to users.
Use the MOUNT clause to mount the database. Do not use this clause when the database is mounted.
Specify MOUNT STANDBY DATABASE to mount a physical standby database. As soon as this statement executes, the standby instance can receive archived redo logs from the primary instance and can archive the logs to the STANDBY_ARCHIVE_DEST location.
Specify MOUNT CLONE DATABASE to mount the clone database.
| See Also:
Oracle9i User-Managed Backup and Recovery Guide for more information on clone databases |
Use the OPEN clause to make the database available for normal use. You must mount the database before you can open it.
If you specify only OPEN, without any other keywords, the default is OPEN READ WRITE NORESETLOGS.
Specify READ WRITE to open the database in read/write mode, allowing users to generate redo logs. This is the default.
Specify RESETLOGS to reset the current log sequence number to 1 and discards any redo information that was not applied during recovery, ensuring that it will never be applied. This effectively discards all changes that are in the redo log, but not in the database.
You must specify RESETLOGS to open the database after performing media recovery with an incomplete recovery using the RECOVER clause or with a backup control file. After opening the database with this clause, you should perform a complete database backup.
Specify NORESETLOGS to retain the current state of the log sequence number and redo log files.
You can specify RESETLOGS and NORESETLOGS only after performing incomplete media recovery or complete media recovery with a backup control file. In any other case, Oracle uses the NORESETLOGS automatically.
Use the MIGRATE clause only if you are upgrading from Oracle release 7.3.4 to the current release. This clause instructs Oracle to modify system parameters dynamically as required for the upgrade. For upgrade from releases other than 7.3.4, you can use the SQL*Plus STARTUP MIGRATE command.
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Specify READ ONLY to restrict users to read-only transactions, preventing them from generating redo logs. You can use this clause to make a physical standby database available for queries even while archive logs are being copied from the primary database site.
READ ONLY if it is currently opened READ WRITE by another instance.READ ONLY if it requires recovery.READ ONLY. However, you can take datafiles offline and online, and you can recover offline datafiles and tablespaces while the database is open READ ONLY.The recovery_clauses include post-backup operations.
| See Also:
Oracle9i Backup and Recovery Concepts and Oracle9i Recovery Manager User's Guide for information on backing up the database and "Database Recovery: Examples" |
The general_recovery clause lets you control media recovery for the database or standby database, or for specified tablespaces or files. You can use this clause when your instance has the database mounted, open or closed, and the files involved are not in use.
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Note: If you do not have special media requirements, Oracle Corporation recommends that you use the SQL*Plus |
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Specify AUTOMATIC if you want Oracle to automatically generate the name of the next archived redo log file needed to continue the recovery operation. If the LOG_ARCHIVE_DEST_n parameters are defined, Oracle scans those that are valid and enabled for the first local destination. It uses that destination in conjunction with LOG_ARCHIVE_FORMAT to generate the target redo log filename. If the LOG_ARCHIVE_DEST_n parameters are not defined, Oracle uses the value of the LOG_ARCHIVE_DEST parameter instead.
If the resulting file is found, Oracle applies the redo contained in that file. If the file is not found, Oracle prompts you for a filename, displaying the generated filename as a suggestion.
If you specify neither AUTOMATIC nor LOGFILE, Oracle prompts you for a filename, displaying the generated filename as a suggestion. You can then accept the generated filename or replace it with a fully qualified filename. If you know that the archived filename differs from what Oracle would generate, you can save time by using the LOGFILE clause.
Specify FROM 'location' to indicate the location from which the archived redo log file group is read. The value of location must be a fully specified file location following the conventions of your operating system. If you omit this parameter, Oracle assumes that the archived redo log file group is in the location specified by the initialization parameter LOG_ARCHIVE_DEST or LOG_ARCHIVE_DEST_1.
The full_database_recovery clause lets you recover an entire database.
Specify the DATABASE clause to recover the entire database. This is the default. You can use this clause only when the database is closed.
Specify the STANDBY DATABASE clause to manually recover a physical standby database using the control file and archived redo log files copied from the primary database. The standby database must be mounted but not open.
UNTIL clause to specify the duration of the recovery operation.
CANCEL indicates cancel-based recovery. This clause recovers the database until you issue the ALTER DATABASE statement with the RECOVER CANCEL clause.TIME indicates time-based recovery. This parameter recovers the database to the time specified by the date. The date must be a character literal in the format 'YYYY-MM-DD:HH24:MI:SS'.CHANGE indicates change-based recovery. This parameter recovers the database to a transaction-consistent state immediately before the system change number (SCN) specified by integer.USING BACKUP CONTROLFILE if you want to use a backup control file instead of the current control file.The partial_database_recovery clause lets you recover individual tablespaces and datafiles.
Specify the TABLESPACE clause to recover only the specified tablespaces. You can use this clause if the database is open or closed, provided the tablespaces to be recovered are offline.
Specify the DATAFILE clause to recover the specified datafiles. You can use this clause when the database is open or closed, provided the datafiles to be recovered are offline.
You can identify the datafile by name or by number. If you identify it by number, then filenumber is an integer representing the number found in the FILE# column of the V$DATAFILE dynamic performance view or in the FILE_ID column of the DBA_DATA_FILES data dictionary view.
Specify STANDBY TABLESPACE to reconstruct a lost or damaged tablespace in the standby database using archived redo log files copied from the primary database and a control file.
Specify STANDBY DATAFILE to manually reconstruct a lost or damaged datafile in the physical standby database using archived redo log files copied from the primary database and a control file. You can identify the file by name or by number, as described for the DATAFILE clause.
UNTIL [CONSISTENT WITH] CONTROLFILE if you want the recovery of an old standby datafile or tablespace to use the current standby database control file. However, any redo in advance of the standby controlfile will not be applied. The keywords CONSISTENT WITH are optional and are provided for semantic clarity.Specify the LOGFILE 'filename' to continue media recovery by applying the specified redo log file.
Use the TEST clause to conduct a trial recovery. A trial recovery is useful if a normal recovery procedure has encountered some problem. It lets you look ahead into the redo stream to detect possible additional problems. The trial recovery applies redo in a way similar to normal recovery, but it does not write changes to disk, and it rolls back its changes at the end of the trial recovery.
The ALLOW integer CORRUPTION clause lets you specify, in the event of logfile corruption, the number of corrupt blocks that can be tolerated while allowing recovery to proceed.
When you use this clause during trial recovery (that is, in conjunction with the TEST clause), integer can exceed 1. When using this clause during normal recovery, integer cannot exceed 1.
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Use the PARALLEL clause to specify whether the recovery of media will be parallelized.
Specify NOPARALLEL for serial execution. This is the default.
Specify PARALLEL if you want Oracle to select a degree of parallelism equal to the number of CPUs available on all participating instances times the value of the PARALLEL_THREADS_PER_CPU initialization parameter.
Specification of integer indicates the degree of parallelism, which is the number of parallel threads used in the parallel operation. Each parallel thread may use one or two parallel execution servers. Normally Oracle calculates the optimum degree of parallelism, so it is not necessary for you to specify integer.
| See Also:
"Notes on the parallel_clause" for |
Specify CONTINUE to continue multi-instance recovery after it has been interrupted to disable a thread.
Specify CONTINUE DEFAULT to continue recovery using the redo log file that Oracle would automatically generate if no other logfile were specified. This clause is equivalent to specifying AUTOMATIC, except that Oracle does not prompt for a filename.
Specify CANCEL to terminate cancel-based recovery.
The managed_standby_recovery clause applies to physical standby only. Use it to specify managed standby recovery mode. This mode assumes that the managed standby database is an active component of an overall standby database architecture. A primary database actively archives its redo log files to the standby site. As these archived redo logs arrive at the standby site, they become available for use by a managed standby recovery operation. Managed standby recovery is restricted to media recovery. You can use this clause when your instance has the database mounted, open or closed, and the files involved are not in use.
The same restrictions apply as are listed under general_recovery.
| See Also:
Oracle Data Guard Concepts and Administration for more information on the parameters of this clause "Recovering a Managed Standby Database: Examples" |
Specify DISCONNECT to indicate that the managed redo process (MRP), an Oracle background process, should apply archived redo files as a detached background process. Doing so leaves the current session available for other tasks. (The FROM SESSION keywords are optional and are provided for semantic clarity.)
DISCONNECT only when you are initiating managed standby recovery. You cannot specify it after the operation has started.TIMEOUT and DISCONNECT [FROM SESSION]. TIMEOUT applies only to foreground recovery operations, whereas the DISCONNECT clause initiates background recovery operations.Specify in minutes the wait period of the managed recovery operation. The recovery process waits for integer minutes for a requested archived log redo to be available for writing to the managed standby database. If the redo log file does not become available within that time, the recovery process terminates with an error message. You can then issue the statement again to return to managed standby recovery mode.
If you omit TIMEOUT or if you specify NOTIMEOUT, the database remains in managed standby recovery mode until you reissue the statement with the RECOVER CANCEL clause or until instance shutdown or failure.
TIMEOUT, you cannot also specify FINISH.TIMEOUT and DISCONNECT [FROM SESSION]. TIMEOUT applies only to foreground recovery operations, whereas the DISCONNECT clause initiates background recovery operations.Specify DELAY to instruct Oracle to wait the specified interval (in minutes) before applying the archived redo logs. The delay interval begins after the archived redo logs have been selected for recovery.
NODELAY if the need arises to apply a delayed archivelog immediately on the standby database.DEFAULT DELAY to revert to the number of minutes specified in the LOG_ARCHIVE_DEST_n initialization parameter on the primary database.Both of these parameters override any setting of DELAY in the LOG_ARCHIVE_DEST_n parameter on the primary database. If you specify neither of these parameters, application of the archivelog is delayed according to the LOG_ARCHIVE_DEST_n setting. If DELAY was not specified in that parameter, the archivelog is applied immediately.
NODELAY and DELAY.DELAY, you cannot also specify FINISH.
| See Also:
Oracle9i Database Reference for detailed information on the |
Use the NEXT parameter to apply the specified number of archived redo logs as soon as possible after they have been archived. This parameter temporarily overrides any delay setting in the LOG_ARCHIVE_DEST_n initialization parameter on the primary database and over any DELAY values specified in an earlier ALTER DATABASE ... managed_standby_recovery statement. Once the integer archived redo logs are processed, any such delay again takes effect.
If you specify NEXT, you cannot also specify FINISH.
| See Also:
Oracle9i Database Reference for detailed information on the |
Specify the number of minutes from the current time after which the managed recovery operation terminates automatically. The process may actually expire after the interval specified, because Oracle will finish processing any archived redo log that is being processed at the expiration time.
Specify NOEXPIRE to disable a previously specified EXPIRE option.
Expiration is always relative to the time the current statement is issued rather than to the start time of the managed recovery process. To terminate an existing managed recovery operation, use the CANCEL parameter.
If you specify EXPIRE, you cannot also specify FINISH.
Use this clause to instruct Oracle when to terminate managed recovery.
THROUGH ... SEQUENCE: Specify this clause if you want Oracle to terminate managed recovery based on thread number and sequence number of an archivelog. Once the corresponding archivelog has been applied, managed recovery terminates. If you omit the THREAD clause, Oracle assumes thread 1.THROUGH ALL ARCHIVELOG: Specify this clause if you want Oracle to continue the managed standby process until all archivelogs have been recovered. You can use this statement to override an earlier statement that specified THROUGH ... SEQUENCE. If you omit the THROUGH clause entirely, this is the default.THROUGH ... SWITCHOVER: The managed standby recovery process normally stops when it encounters a switchover operation, because these operations produce an "end-of-redo archival" indicator. This clause is useful if you have more than one standby database, all but one of which will remain in the standby role after the switchover. This clause keeps the managed standby recovery process operational. It lets these "secondary" standby databases wait to receive the redo stream from the new primary database, rather than stopping the recovery process and then starting it again after the new primary database is activated.
ALL to keep managed standby recovery operational through all switchover operations.LAST to cancel managed standby recovery operations after the final end-of-redo archival indicator.NEXT to cancel managed standby recovery after recovering the next end-of-redo archival indicator encountered. This is the default.Specify CANCEL to terminate the managed standby recovery operation after applying all the redo in the current archived redo file. If you specify only the CANCEL keyword, session control returns when the recovery process actually terminates.
CANCEL IMMEDIATE to terminate the managed recovery operation after applying all the redo in the current archived redo file or after the next redo log file read, whichever comes first. Session control returns when the recovery process actually terminates.The CANCEL IMMEDIATE clause cannot be issued from the same session that issued the RECOVER MANAGED STANDBY DATABASE statement.
CANCEL IMMEDIATE NOWAIT is the same as CANCEL IMMEDIATE except that session control returns immediately, not after the recovery process terminates.CANCEL NOWAIT terminates the managed recovery operation after the next redo log file read and returns session control immediately.The FINISH clause applies only to physical standby databases. Specify FINISH to recover the current standby online redo logfiles of the standby database. Use this clause only in the event of the failure of the primary database, when the logwriter (LGWR) process has been transmitting redo to the standby current logs. This clause overrides any delay intervals specified for the archivelogs, so that Oracle applies the logs immediately.
After the FINISH operation, you must open the standby database as the primary database.
Specify NOWAIT to have control returned immediately rather than after the recovery process is complete.
You cannot specify FINISH if you have also specified TIMEOUT, DELAY, EXPIRE, or NEXT.
Use the parallel_clause to indicate whether Oracle should parallelize the managed recovery processes. If you specify NOPARALLEL or omit this clause entirely, Oracle performs the managed standby recovery operation serially.
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Specify END BACKUP to take out of online backup mode any datafiles in the database currently in online backup mode. The database must be mounted but not open when you perform this operation.
You can end online ("hot") backup operations in three ways. During normal operation, you can take a tablespace out of online backup mode using the ALTER TABLESPACE ... END BACKUP statement. Doing so avoids the increased overhead of leaving the tablespace in online backup mode.
After a system failure, instance failure, or SHUTDOWN ABORT operation, Oracle does not know whether the files in online backup mode match the files at the time the system crashed. If you know the files are consistent, you can take either individual datafiles or all datafiles out of online backup mode. Doing so avoids media recovery of the files upon startup.
ALTER DATABASE DATAFILE ... END BACKUP statement. See database_file_clauses.ALTER TABLESPACE ... END BACKUP statement.
| See Also:
ALTER TABLESPACE for information on ending online tablespace backup |
The database_file_clauses let you modify datafiles and tempfiles. You can use any of the following clauses when your instance has the database mounted, open or closed, and the files involved are not in use.
Use the CREATE DATAFILE clause to create a new empty datafile in place of an old one. You can use this clause to re-create a datafile that was lost with no backup. The filename or filenumber must identify a file that is or was once part of the database. If you identify the file by number, then filenumber is an integer representing the number found in the FILE# column of the V$DATAFILE dynamic performance view or in the FILE_ID column of the DBA_DATA_FILES data dictionary view.
AS NEW to create an Oracle-managed datafile with a system-generated filename, the same size as the file being replaced, in the default file system location for datafiles.AS datafile_tempfile_spec to assign a filename (and optional size) for the new datafile.If the original file (filename or filenumber) is an existing Oracle-managed datafile, then Oracle attempts to delete the original file after creating the new file. If the original file is an existing user-managed datafile, Oracle does not attempt to delete the original file.
If you omit the AS clause entirely, Oracle creates the new file with the same name and size as the file specified by filename or filenumber.
During recovery, all archived redo logs written to since the original datafile was created must be applied to the new, empty version of the lost datafile.
Oracle creates the new file in the same state as the old file when it was created. You must perform media recovery on the new file to return it to the state of the old file at the time it was lost.
SYSTEM tablespace.autoextend_clause of datafile_tempfile_spec in this CREATE DATAFILE clause.
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The DATAFILE clauses let you manipulate a file that you identify by name or by number. If you identify it by number, then filenumber is an integer representing the number found in the FILE# column of the V$DATAFILE dynamic performance view or in the FILE_ID column of the DBA_DATA_FILES data dictionary view. The DATAFILE clauses affect your database files as follows:
Specify ONLINE to bring the datafile online.
Specify OFFLINE to take the datafile offline. If the database is open, you must perform media recovery on the datafile before bringing it back online, because a checkpoint is not performed on the datafile before it is taken offline.
If the database is in NOARCHIVELOG mode, you must specify the DROP clause to take a datafile offline. However, the DROP clause does not remove the datafile from the database. To do that, you must drop the tablespace in which the datafile resides. Until you do so, the datafile remains in the data dictionary with the status RECOVER or OFFLINE.
If the database is in ARCHIVELOG mode, Oracle ignores the DROP keyword.
Specify RESIZE if you want Oracle to attempt to increase or decrease the size of the datafile to the specified absolute size in bytes. Use K or M to specify this size in kilobytes or megabytes. There is no default, so you must specify a size.
If sufficient disk space is not available for the increased size, or if the file contains data beyond the specified decreased size, Oracle returns an error.
Specify END BACKUP to take the datafile out of online backup mode. The END BACKUP clause is described more fully at the top level of the syntax of ALTER DATABASE. See "END BACKUP Clause".
Use the TEMPFILE clause to resize your temporary datafile or specify the autoextend_clause, with the same effect as with a permanent datafile. You can identify the tempfile by name or by number. If you identify it by number, then filenumber is an integer representing the number found in the FILE# column of the V$TEMPFILE dynamic performance view.
You cannot specify TEMPFILE unless the database is open.
Specify DROP to drop tempfile from the database. The tablespace remains.
If you specify INCLUDING DATAFILES, Oracle also deletes the associated operating system files and writes a message to the alert log for each such deleted file.
Use the autoextend_clause to enable or disable the automatic extension of a new datafile or tempfile.
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Use the RENAME FILE clause to rename datafiles, tempfiles, or redo log file members. You must create each filename using the conventions for filenames on your operating system before specifying this clause.
This clause renames only files in the control file. It does not actually rename them on your operating system. The operating system files continue to exist, but Oracle no longer uses them. If the old files were Oracle managed, Oracle drops the old operating system file after this statement executes, because the control file no longer points to them as datafiles, tempfiles, or redo log files.
The logfile clauses let you add, drop, or modify log files.
Use the ARCHIVELOG clause and NOARCHIVELOG clause only if your instance has the database mounted but not open, with Real Application Clusters disabled.
Specify ARCHIVELOG if you want the contents of a redo log file group to be archived before the group can be reused. This mode prepares for the possibility of media recovery. Use this clause only after shutting down your instance normally, or immediately with no errors, and then restarting it and mounting the database with Real Application Clusters disabled.
Specify NOARCHIVELOG if you do not want the contents of a redo log file group to be archived so that the group can be reused. This mode does not prepare for recovery after media failure.
Use this clause to put the database into or take the database out of FORCE LOGGING mode. The database must be mounted or open.
In FORCE LOGGING mode, Oracle will log all changes in the database except for changes in 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 specify FORCE LOGGING, Oracle waits for all ongoing unlogged operations to finish.
| See Also:
Oracle9i Database Administrator's Guide for information on when to use |
Use the ADD LOGFILE clause to add one or more redo log file groups to the specified thread, making them available to the instance assigned the thread. If you specify STANDBY, the redo log file created is for use by physical standby databases only.
To learn whether a logfile has been designated for online or standby database use, query the TYPE column of the V$LOGFILE dynamic performance view.
The THREAD clause is applicable only if you are using Oracle with the Real Application Clusters option in parallel mode. integer is the thread number. The number of threads you can create is limited by the value of the MAXINSTANCES parameter specified in the CREATE DATABASE statement.
If you omit THREAD, the redo log file group is added to the thread assigned to your instance.
The GROUP clause uniquely identifies the redo log file group among all groups in all threads and can range from 1 to the MAXLOGFILES value. You cannot add multiple redo log file groups having the same GROUP value. If you omit this parameter, Oracle generates its value automatically. You can examine the GROUP value for a redo log file group through the dynamic performance view V$LOG.
Each redo_log_file_spec specifies a redo log file group containing one or more members (that is, one or more copies).
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Use the DROP LOGFILE clause to drop all members of a redo log file group. Specify a redo log file group as indicated for the ADD LOGFILE MEMBER clause.
ALTER SYSTEM SWITCH LOGFILE statement.Use the ADD LOGFILE MEMBER clause to add new members to existing redo log file groups. Each new member is specified by 'filename'. If the file already exists, it must be the same size as the other group members, and you must specify REUSE. If the file does not exist, Oracle creates a file of the correct size. You cannot add a member to a group if all of the group's members have been lost through media failure.
You can specify STANDBY for symmetry, to indicate that the logfile member is for use only by a physical standby database. However, this keyword is not required. If group integer was added for standby database use, all of its members will be used only for standby databases as well.
You can specify an existing redo log file group in one of two ways:
Specify the value of the GROUP parameter that identifies the redo log file group.
List all members of the redo log file group. You must fully specify each filename according to the conventions of your operating system.
Use the DROP LOGFILE MEMBER clause to drop one or more redo log file members. Each 'filename' must fully specify a member using the conventions for filenames on your operating system.
ALTER SYSTEM SWITCH LOGFILE statement.
DROP LOGFILE clause.
Specify the ADD SUPPLEMENTAL LOG DATA clause to place additional column data into the log stream any time an update operation is performed. These four keywords alone enable minimal supplemental logging, which is not enabled by default.
Minimal supplemental logging ensures that Logminer (and any products building on Logminer technology) will have sufficient information to support chained rows and various storage arrangements such as cluster tables.
If supplemental log data will be the source of change in another database, such as a logical standby, the log data must also uniquely identify each row updated. In this case, you should enable identification key ("full") supplemental logging by specifying PRIMARY KEY COLUMNS and UNIQUE KEY COLUMNS.
When you specify PRIMARY KEY COLUMNS, Oracle ensures, for all tables with a primary key, that all columns of the primary key are placed into the redo log whenever an update operation is performed. If no primary key is defined, Oracle places into the redo log a set of columns that uniquely identifies the row. This set may include all columns with a fixed-length maximum size.
When you specify UNIQUE INDEX COLUMNS, Oracle ensures, for all tables with a unique key, that if any unique key columns are modified, all other columns belonging to the unique key are also placed into the redo log.
| See Also:
Oracle Data Guard Concepts and Administration for information on supplemental logging |
Use the DROP SUPPLEMENTAL LOG DATA clause to instruct Oracle to stop placing additional log information into the redo log stream whenever an update operation occurs. This statement terminates the effect of a previous ADD SUPPLEMENTAL LOG DATA statement.
| See Also:
Oracle Data Guard Concepts and Administration for information on supplemental logging |
Use the CLEAR LOGFILE clause to reinitialize an online redo log, optionally without archiving the redo log. CLEAR LOGFILE is similar to adding and dropping a redo log, except that the statement may be issued even if there are only two logs for the thread and also may be issued for the current redo log of a closed thread.
UNARCHIVED if you want to reuse a redo log that was not archived.
UNRECOVERABLE DATAFILE if you have taken the datafile offline with the database in ARCHIVELOG mode (that is, you specified ALTER DATABASE ... DATAFILE OFFLINE without the DROP keyword), and if the unarchived log to be cleared is needed to recover the datafile before bringing it back online. In this case, you must drop the datafile and the entire tablespace once the CLEAR LOGFILE statement completes.
Do not use CLEAR LOGFILE to clear a log needed for media recovery. If it is necessary to clear a log containing redo after the database checkpoint, you must first perform incomplete media recovery. The current redo log of an open thread can be cleared. The current log of a closed thread can be cleared by switching logs in the closed thread.
If the CLEAR LOGFILE statement is interrupted by a system or instance failure, then the database may hang. If this occurs, reissue the statement after the database is restarted. If the failure occurred because of I/O errors accessing one member of a log group, then that member can be dropped and other members added.
The controlfile_clauses let you create or back up a control file.
The CREATE STANDBY CONTROLFILE clause applies only to physical standby databases. Use this clause to create a control file to be used to maintain a physical standby database. If the file already exists, you must specify REUSE.
Use the BACKUP CONTROLFILE clause to back up the current control file. The database must be open or mounted when you specify this clause.
Specify the file to which the control file is backed up. You must fully specify the filename using the conventions for your operating system. If the specified file already exists, you must specify REUSE.
Specify TO TRACE if you want Oracle to write SQL statements to a trace file rather than making a physical backup of the control file. You can use SQL statements written to the trace file to start up the database, re-create the control file, and recover and open the database appropriately, based on the created control file.
You can copy the statements from the trace file into a script file, edit the statements as necessary, and use the script if all copies of the control file are lost (or to change the size of the control file).
AS filename if you want Oracle to place the script into a file called filename rather than into the standard trace file.REUSE to allow Oracle to overwrite any existing file called filename.RESETLOGS indicates that the SQL statement written to the trace file for starting the database is ALTER DATABASE OPEN RESETLOGS. This setting is valid only if the online logs are unavailable.NORESETLOGS indicates that the SQL statement written to the trace file for starting the database is ALTER DATABASE OPEN NORESETLOGS. This setting is valid only if all the online logs are available.If you cannot predict the future state of the online logs, specify neither RESETLOGS nor NORESETLOGS. In this case, Oracle puts both versions of the script into the trace file, and you can choose which version is appropriate when the script becomes necessary.
Use these clauses to activate the standby database or to specify whether it is in protected or unprotected mode.
| See Also:
Oracle Data Guard Concepts and Administration for descriptions of physical and logical the standby database and for information on maintaining and using standby databases |
The ACTIVATE STANDBY DATABASE clause changes the state of a standby database to an active database and prepares it to become the primary database. The database must be mounted before you can specify this clause.
Specify PHYSICAL to activate a physical standby database. This is the default.
Specify LOGICAL to activate a logical standby database. If you have more than one logical standby database, you should first ensure that the same log data is available on all the standby systems.
This clause applies only to physical standby databases. Use this clause to force the operation to proceed even if standby redo logfiles contain data that could be recovered using the RECOVER MANAGED STANDBY DATABASE FINISH command.
Use this clause to specify the level of protection for the data in your database environment. You specify this clause from the primary database, which must be mounted but not open.
This setting establishes "maximum protection mode" and offers the highest level of data protection. A transaction does not commit until all data needed to recover that transaction has been written to at least one physical standby database that is configured to use the SYNC log transport mode. If the primary database is unable to write the redo records to at least one such standby database, the primary database is shut down. This mode guarantees zero data loss, but it has the greatest potential impact on the performance and availability of the primary database.
This setting establishes "maximum availability mode" and offers the next highest level of data protection. A transaction does not commit until all data needed to recover that transaction has been written to at least one (physical or logical) standby database that is configured to use the SYNC log transport mode. Unlike maximum protection mode, the primary database does not shut down if it is unable to write the redo records to at least one such standby database. Instead, the protection is lowered to maximum performance mode until the fault has been corrected and the standby database has caught up with the primary database. This mode guarantees zero data loss unless the primary database fails while in maximum performance mode. Maximum availability mode provides the highest level of data protection that is possible without affecting the availability of the primary database.
This setting establishes "maximum performance mode" and is the default setting. A transaction commits before the data needed to recover that transaction has been written to a standby database. Therefore, some transactions may be lost if the primary database fails and you are unable to recover the redo records from the primary database. This mode provides the highest level of data protection that is possible without affecting the performance of the primary database.
To determine the current mode of the database, query the PROTECTION_MODE column of the V$DATABASE dynamic performance view.
| See Also:
Oracle Data Guard Concepts and Administration for full information on using these standby database settings |
Specify the REGISTER LOGFILE clause from the standby database to manually register log files from the failed primary.
For a logical standby database, you can use this command to seed the initial starting point for a new logical standby database. Then when you issue an ALTER DATABASE START LOGICAL STANDBY APPLY INITIAL command, Oracle will use the lowest registered logfile as its starting point.
Specify OR REPLACE to allow an existing archivelog entry in the standby database to be updated, for example, when its location or file specification changes. The SCNs of the entries must match exactly, and the original entry must have been created by the managed standby log transmittal mechanism.
Use this clause to perform a "graceful switchover", in which the current primary database take on standby status, and one standby database becomes the primary database. In a Real Application Clusters environment, all instances other than the instance from which you issue this statement must be shutdown normally.
PHYSICAL to prepare the primary database to run in the role of a physical standby database.LOGICAL to prepare the primary database to run in the role of a logical standby database. If you specify LOGICAL, you must then issue an ALTER DATABASE START LOGICAL STANDBY APPLY statement.COMMIT TO SWITCHOVER TO STANDBY to perform a graceful database switchover of the primary database to standby database status. The primary database must be open.COMMIT TO SWITCHOVER TO PRIMARY statement to perform a graceful switchover of this standby database to primary status. The standby database must be mounted or open in READ ONLY mode.If you specify WITH SESSION SHUTDOWN, Oracle shuts down any open application sessions and rolls back uncommitted transactions as part of the execution of this statement. If you omit this clause or specify WITHOUT SESSION SHUTDOWN (which is the default), the statement will fail if any application sessions are open.
This clause is not necessary or supported for a logical database.
Specify WAIT if you want Oracle to return control after the completion of the SWITCHOVER command. Specify NOWAIT if you want Oracle to return control before the switchover operation is complete. the default is WAIT.
| See Also:
Oracle Data Guard Concepts and Administration for full information on graceful switchover between primary and standby databases |
Specify the START LOGICAL STANDBY APPLY clause to begin applying redo logs to a logical standby database.
INITIAL the first time you apply the logs to the standby database.NEW PRIMARY after the ALTER DATABASE COMMIT TO SWITCHOVER TO LOGICAL STANDBY statement or when a standby database has completed processing logs from one primary and now a new database becomes the primary.Use this clause to stop the log apply services. This clause applies only to logical standby databases, not to physical standby databases. Use the STOP clause to stop the apply in an orderly fashion.
Use these clauses to modify the default settings of the database.
CHARACTER SET changes the character set the database uses to store data. NATIONAL CHARACTER SET changes the national character set used to store data in columns specifically defined as NCHAR, NCLOB, or NVARCHAR2. Specify character_set without quotation marks. The database must be open.
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Cautions:
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In Oracle9i, CLOB data is stored as UCS-2 (two-byte fixed-width Unicode) for multibyte database character sets. For single-byte database character sets, CLOB data is stored in the database character set. When you change the database or national character set with an ALTER DATABASE statement, no data conversion is performed. Therefore, if you change the database character set from single byte to multibyte using this statement, CLOB columns will remain in the original database character set. This may introduce data inconsistency in your CLOB columns. Likewise, if you change the national character set from one Unicode set to another, your SQL NCHAR columns (NCHAR, NVARCHAR2, NCLOB) may be corrupted.
The recommended procedure for changing database character sets is:
CLOB and SQL NCHAR datatype columns.CLOB and SQL NCHAR columns.ALTER DATABASE statements to change the character set and national character set.CLOB and SQL NCHAR columns.SYSDBA system privilege, and you must start up the database in restricted mode (for example, with the SQL*Plus STARTUP RESTRICT command).| See Also:
Oracle9i Database Globalization Support Guide for information on database character set migration and "Changing a Character Set: Example" |
Use the SET TIME_ZONE clause to set the time zone of the database. You can specify the time zone in two ways:
hh:mm is -12:00 to +14:00.TZNAME column of the V$TIMEZONE_NAMES dynamic performance view.
| See Also:
Oracle9i Database Reference for information on the dynamic performance views |
Oracle normalizes all new TIMESTAMP WITH LOCAL TIME ZONE data to the time zone of the database when the data is stored on disk. Oracle does not automatically update existing data in the database to the new time zone. To determine the time zone of the database, query the built-in function DBTIMEZONE (see DBTIMEZONE).
After setting or changing the time zone with this clause, you must restart the database for the new time zone to take effect.
Specify this clause to change the default temporary tablespace of the database. After this operation completes, Oracle automatically reassigns to the new default temporary tablespace all users who had been assigned to the old default temporary tablespace. You can then drop the old default temporary tablespace if you wish.
To learn the name of the current default temporary tablespace, query the PROPERTY_VALUE column of the DATABASE_PROPERTIES data dictionary table where the PROPERTY_NAME = 'DEFAULT_TEMP_TABLESPACE'.
SYSTEM tablespace is locally managed, the tablespace you specify as the default temporary tablespace must also be locally managed.
Specify RESET COMPATIBILITY to mark the database to be reset to an earlier version of Oracle when the database is next restarted. The database must be open.
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Note:
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| See Also:
Oracle9i Database Migration Guide for more information on downgrading to an earlier version of Oracle |
Use the CONVERT clause to complete the conversion of the Oracle7 data dictionary. After you use this clause, the Oracle7 data dictionary no longer exists in the Oracle database.
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Note: Use this clause only when you are migrating to Oracle9i, and do not use this clause when the database is mounted. |
Use these clauses to enable and disable the thread of redo log file groups.
In an Oracle Real Application Clusters environment, specify ENABLE THREAD to enable the specified thread of redo log file groups. The thread must have at least two redo log file groups before you can enable it. The database must be open.
Specify PUBLIC to make the enabled thread available to any instance that does not explicitly request a specific thread with the initialization parameter THREAD. If you omit PUBLIC, the thread is available only to the instance that explicitly requests it with the initialization parameter THREAD.
| See Also:
Oracle9i Real Application Clusters Administration for more information on enabling and disabling threads |
Specify DISABLE THREAD to disable the specified thread, making it unavailable to all instances. The database must be open, but you cannot disable a thread if an instance using it has the database mounted.
| See Also:
Oracle9i Real Application Clusters Administration for more information on enabling and disabling threads and "Disabling and Enabling a Real Application Clusters Thread: Examples" |
Specify RENAME GLOBAL_NAME to change the global name of the database. The database is the new database name and can be as long as eight bytes. The optional domain specifies where the database is effectively located in the network hierarchy. Do not use this clause when the database is mounted.
| See Also:
Oracle9i Heterogeneous Connectivity Administrator's Guide for more information on global names and "Changing the Global Database Name: Example" |
Use the security_clause (GUARD) to protect data in the database from being changed.
Specify ALL to prevent all users other than SYS from making changes to any data in the database.
Specify STANDBY to prevent all users other than SYS from making changes to any database object being maintained by logical standby. This setting is useful if you want report operations to be able to modify data as long as it is not being replicated by logical standby.
| See Also:
Oracle Data Guard Concepts and Administration for information on logical standby |
Specify NONE if you want normal security for all data in the database.
The first statement that follows opens the database in read-only mode. The second statement returns the database to read/write mode and clears the online redo logs:
ALTER DATABASE OPEN READ ONLY; ALTER DATABASE OPEN READ WRITE RESETLOGS;
The following statement performs tablespace recovery using parallel recovery processes:
ALTER DATABASE RECOVER TABLESPACE tbs_03 PARALLEL;
The following statement adds a redo log file group with two members and identifies it with a GROUP parameter value of 3:
ALTER DATABASE ADD LOGFILE GROUP 3 ('diska:log3.log' , 'diskb:log3.log') SIZE 50K;
The following statement adds a redo log file group containing two members to thread 5 (in a Real Application Clusters environment) and assigns it a GROUP parameter value of 4:
ALTER DATABASE ADD LOGFILE THREAD 5 GROUP 4 ('diska:log4.log', 'diskb:log4:log');
The following statement drops one redo log file member added in the previous example:
ALTER DATABASE DROP LOGFILE MEMBER 'diskb:log3.log';
The following statement drops all members of the redo log file group 3:
ALTER DATABASE DROP LOGFILE GROUP 3;
The following statement adds a member to the redo log file group added in the previous example:
ALTER DATABASE ADD LOGFILE MEMBER 'diskc:log3.log' TO GROUP 3;
The following statement renames a redo log file member:
ALTER DATABASE RENAME FILE 'diskc:log3.log' TO 'diskb:log3.log';
The preceding statement only changes the member of the redo log group from one file to another. The statement does not actually change the name of the file 'diskc:log3.log' to 'diskb:log3.log'. You must perform this operation through your operating system.
The following statement makes the tbs_5 tablespace the default temporary tablespace of the database. This statement either establishes a default temporary tablespace if none was specified at create time, or replaces an existing default temporary tablespace with temp:
ALTER DATABASE DEFAULT TEMPORARY TABLESPACE tbs_5;
The following statement disables thread 5 in a Real Application Clusters environment:
ALTER DATABASE DISABLE THREAD 5;
The following statement enables thread 5 in a Real Application Clusters environment, making it available to any Oracle instance that does not explicitly request a specific thread:
ALTER DATABASE ENABLE PUBLIC THREAD 5;
The following statement creates a new datafile 'tabspace_file04.dbf' based on the file 'tabspace_file03.dbf'. Before creating the new datafile, you must take the existing datafile (or the tablespace in which it resides) offline.
ALTER DATABASE CREATE DATAFILE 'tbs_f03.dbf' AS 'tbs_f04.dbf';
The following statement changes the global name of the database and includes both the database name and domain:
ALTER DATABASE RENAME GLOBAL_NAME TO demo.world.oracle.com;
The following statements change the database character set and national character set to the UTF8 character set:
ALTER DATABASE CHARACTER SET UTF8; ALTER DATABASE NATIONAL CHARACTER SET UTF8;
The database name is optional, and the character set name is specified without quotation marks.
The following statement attempts to change the size of datafile 'disk1:db1.dat':
ALTER DATABASE DATAFILE 'disk1:db1.dat' RESIZE 10 M;
The following statement clears a log file:
ALTER DATABASE CLEAR LOGFILE 'diskc:log3.log';
The following statement performs complete recovery of the entire database, letting Oracle generate the name of the next archived redo log file needed:
ALTER DATABASE RECOVER AUTOMATIC DATABASE;
The following statement explicitly names a redo log file for Oracle to apply:
ALTER DATABASE RECOVER LOGFILE 'diskc:log3.log';
The following statement recovers the standby datafile /finance/stbs_21.f, using the corresponding datafile in the original standby database, plus all relevant archived logs and the current standby database control file:
ALTER DATABASE RECOVER STANDBY DATAFILE '/finance/stbs_21.f' UNTIL CONTROLFILE;
The following statement performs time-based recovery of the database:
ALTER DATABASE RECOVER AUTOMATIC UNTIL TIME '2001-10-27:14:00:00';
Oracle recovers the database until 2:00 p.m. on October 27, 2001.
For an example of recovering a tablespace, see "Using Parallel Recovery Processes: Example".
The following statement recovers the standby database in managed standby recovery mode:
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE;
The following statement puts the database in managed standby recovery mode. The managed recovery process will wait up to 60 minutes for the next archive log:
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE TIMEOUT 60;
If each subsequent log arrives within 60 minutes of the last log, recovery continues indefinitely or until manually terminated.
The following statement terminates the managed recovery operation:
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL IMMEDIATE;
The managed recovery operation terminates before the next group of redo is read from the current redo log file. Media recovery ends in the "middle" of applying redo from the current redo log file.
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