This article describes how to start up a shutdown database in Oracle 11g.

Starting up an Oracle database instance

Assuming you have installed Oracle for the first time and are about to start the database instance. Briefly, this can be done through the three modes NOMOUNT, MOUNT and OPEN. Let us see how it is done.

Database instance startup in NOMOUNT mode

Only during the database creation, recreation of control files, backups and recovery. The instance startup includes the following steps.

Note. SID is the system identifier, by default it is ORCL.

Step 1. Look for the spfileORCL.ora that is present at $ORACLE_HOME/DB.

Step 2. If the file in the Step 1 is not present then look for spfile.ora.

Step 3. And if both files are not present then search for initORCL.ora that contains initialization parameters for the instance also specifying the PFILE parameter during startup and change the default behavior.

Step 4. SGA is allocated.

Step 5. Background Process is started.

Step 6. Alert_ORCL.log files and trace files are created.

Syntax 

STARTUP NOMOUNT PFILE = 'initORCL.ora'

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Database instance startup in MOUNT mode

The following is the procedure to mount a database.

Step 1. In the mount state control files specify in the parameter file provided during startup are located and read.

Step 2. Control files are read to obtain the names and states of the data files andredo log files, but they are not verified for their existence.

Step 3. This state is efficiently used for the specific maintenance operation like

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Database instance startup in OPEN mode

For normal database functions, an instance is started and the database will be mounted and opened. The database in an open mode includes the following tasks

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Syntax for SQL PLUS Database startup

In my next article I will show you the shutdown procedure of the database.