It always used to be a pain in my ass when asked to work on Oracle and Windows.
To have an oracle instance on a Windows Machine, we need to first create a SERVICE for that instance, using the oradim. If the database is created using dbca, dbca would do it for you.
You can see the created service under ControlPanel->AdminstrativeTools->Services.
In Unix/Linux, sqlplus / as sysdba while the db is down would give you the message “Connected to an idle instance”.
But in Windows, if you try to login to the database without the service started, all you will get is “ORA-12560”
C:\Documents and Settings\Administrator>sqlplus / as sysdba
SQL*Plus: Release 10.2.0.1.0 – Production on Thu May 1 17:14:11 2008
Copyright (c) 1982, 2005, Oracle. All rights reserved.
ORA-12560: TNS:protocol adapter error
C:\Documents and Settings\Administrator>
Usually, dbca creates the Oracle service with the option to shutdown the db when the service is stopped and startup when the service is started.
So when you start the OracleService<dbname>, two things happen.
1) the service is started
2) database is also started in open mode.
and viceversa when you stop the service
This is being controlled by the registry entries ORA_<SID>_AUTOSTART and ORA_<SID>_SHUTDOWN under HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\KEY_<oraclehomename> . The default values are TRUE,which will startup and shutdown the DB when ever the service is started or stopped. [These default values will depend on the parameterts used for oradim]
If you only want the service to be start and want to manually STARTUP [NOMOUNT,MOUN,UPGRADE] the db, then change the default value to FALSE.