Starting Up Oracle Database

Oracle Database starts in 3 below steps:

1- No Mount (where it read server parameter (spfile) file).

Connected to an idle instance.

SQL> startup nomount;

ORACLE instance started.

Total System Global Area 1207959552 bytes

Fixed Size                  8620080 bytes

Variable Size             771753936 bytes

Database Buffers          419430400 bytes

Redo Buffers                8155136 bytes

2- Mount (It reads controlfile)

SQL> alter database mount;

Database altered.

3- Open (Also know as read-write mode, where the Database is ready for performing operations)

SQL> alter database open;

Database altered.

SQL> select open_mode from v$database;