This chapter provides a brief overview of the database administration tools available in SQL*Plus, and discusses the following topics:
This chapter is intended for use by database administrators. You must have database administrator privileges to use this functionality.
For more information on database administration, see the Oracle Database Concepts manual.
Special operations such as starting up or shutting down a database are performed by a database administrator (DBA). The DBA has certain privileges that are not assigned to normal users. The commands outlined in this chapter would normally be used by a DBA.
For more information about security and roles in SQL*Plus, see SQL*Plus Security.
An Oracle database may not always be available to all users. To open or close a database, or to start up or shut down an instance, you must have DBA privileges or be connected as SYSOPER or SYSDBA. Other users cannot change the current status of an Oracle database.
Starting a database involves three steps:
Starting an instance
An instance controls the background processes and the allocation of memory area to access an Oracle database.
Mounting the database
Mounting the database associates it with a previously started instance.
Opening the database
Opening the database makes it available for normal database operations.
To start an Oracle Database instance, without mounting the database, enter
To start an instance, mount the database, but leave the database closed, enter
To start an instance using the Oracle Database Server parameter file INITSALES.ORA, mount and open the database named SALES, and restrict access to database administrators, enter
STARTUP OPEN sales PFILE=INITSALES.ORA RESTRICT
where SALES is the database name specified in the DB_NAME parameter in the INITSALES.ORA parameter file.
Shutting down a database involves three steps:
Closing the database
When a database is closed, all database and recovery data in the SGA are written to the datafiles and redo log files, and all online datafiles are closed.
Dismounting the database
Dismounting the database disassociates the database from an instance and closes the control files of the database.
Shutting down the instance
Shutting down an instance reclaims the SGA from memory and terminates the background Oracle Database processes that constitute an Oracle Database instance.
To shut down the database normally after it has been opened and mounted, enter
Database closed. Database dismounted. ORACLE instance shut down.
Every Oracle database has a set of two or more redo log files. The set of redo log files for a database is collectively referred to as the database's redo log.
The redo log is used to record changes made to data. If, for example, there is a database failure, the redo log is used to recover the database. To protect against a failure involving the redo log itself, Oracle Database has a mirrored redo log so that two or more copies of the redo log can be maintained on different disks.
Operating a database in ARCHIVELOG mode enables the archiving of the online redo log.
To automatically begin archiving, enter
ARCHIVE LOG START
To list the details of the current log file being archived, enter
ARCHIVE LOG LIST
Database log mode Archive Mode Automatic archival Enabled Archive destination /vobs/oracle/dbs/arch Oldest online log sequence 221 Next log sequence to archive 222 Current log sequence 222
If a damaged database is in ARCHIVELOG mode, it is a candidate for either complete media recovery or incomplete media recovery operations. To begin media recovery operations use the RECOVER command. For more information about recovering data, see the RECOVER command.
In order to begin recovery operations, you must have DBA privileges.
To recover the database up to a specified time using a control backup file, enter
RECOVER DATABASE UNTIL TIME '1998-11-23:12:47:30'- USING BACKUP CONTROLFILE
To recover two offline tablespaces, enter
RECOVER TABLESPACE ts1, ts2
Make sure that the tablespaces you are interested in recovering have been taken offline, before proceeding with recovery for those tablespaces.