How is an Oracle database opened?

How is an Oracle database opened?

Rating:

The STARTUP command is used to open an Oracle database. Only a database administrator can open an Oracle database. An Oracle database is opened in three stages. First, an Oracle instance is started. Then, the instance mounts the specified database. Finally, the database is opened.

When Oracle starts an instance, it determines the values of the initialization parameters by reading a specified initialization parameter file. After determining the values of the initialization parameters, Oracle allocates a System Global Area (SGA) (a shared memory area that contains data and control information for the instance) and creates background processes.

After getting started, the Oracle instance mounts the specified database to associate the database with the instance. The Oracle instance opens a control file (specified in the CONTROL_FILES initialization parameter of the initialization parameter file) and reads the names of the database's data files and online redo log files.

After mounting the database, the Oracle instance opens the database by opening the database's data files and online redo log files. At this stage, the database is available for normal database operations.

Rating: