Instance and Database Startup

The three steps to starting an Oracle database and making it avilable for system wide use are.

1) Start an instance.

2) Mount the databse.

3) Open the database.

A database administrator can perform these steps using the SQL*PLUS STARTUP statement or Enterprise Manager.

How an Instance is Started

When oracle starts an instance , it reads the intilization parameter file to determine the values of intilization parameters. Then, it allocates an SGA, which is a shared area of memory used for database information, and creates background processes. At this point no database is associated with these memory structures and processes.