Learn about how to start multiple database instances.

1. Start the service for each instance using ORADIM or the Services dialog of the Control Panel.
2. At the command prompt, set the ORACLE_SID configuration parameter to the SID for the first instance to run:

   C:\> SET ORACLE_SID=SID
   

   The variable SID is the name of the Oracle Database instance.

3. Start SQL*Plus:

   C:\> sqlplus /NOLOG
   

4. Connect AS SYSDBA:

   SQL> CONNECT / AS SYSDBA
   

5. Start up the first instance:

   SQL> STARTUP PFILE=ORACLE_BASE\admin\db_name\pfile\init.ora
   

   The variable ORACLE_BASE is c:\app\username (unless you changed it during installation) and db_name is the name of the instance.

6. Repeat Step 2 through Step 5 for the other instances to run.