Oracle Startup Process

The steps that Oracle takes in starting up are as follows:

1. STARTUP NOMOUNT

1.1. Reads the initialization file

1.2. Allocates the shared memory (SGA)

1.3. Starts the background processes

1.4. Opens the alert and trace files

2. ALTER DATABASE MOUNT

2.1. Opens and reads the control files

2.2. Mounts the database and associates the started instance with the database

3. ALTER DATABASE OPEN

3.1. Opens data files and redo logs

3.2. Performs database consistency and auto recovery