Oracle Startup & Shutdown

Oracle start and close is the basic knowledge for Software engineers and DBAs. However when I was asked to interview developers. most of them answer this very ambiguously ,which make me very concern. So this article , I will discuss this so that others can know it more;

Oracle start sequence :

1. Load spfileSID.ora
2. Load spfile.ora
3. Load initSID.ora
4. Load init.ora

Oralce's 4 startup states : 

• SHUTDOWN - Instances & Database all shutdown ,you can run "startup nomount"
• NOMOUNT - Instance is started & memory is allocated to this instance, however the Database is still closed, you can run commands below to check and mount Database: 

                   select * from v$bgprocess;
                   select * from v$instance;

                   alter database mount; 

• MOUNT - Control file is open, however user tables still can't be read, you can run command below to open the Database:

                   alter database open;

• OPEN - the whole database is loaded and open

Shutdown immediate //close the database, back to shutdown status
Startup nomount //enter into nomount state，memory is allocated.show sga.
Startup [nomount | mount | open | force | restrict] [pfile = filename]
Startup restrict; //only user with restrict session right can use the database
Pfile static file ：create pfile=’D:/pfileOrcl.ora’ from spfile;

4 ways to close Oracle :

•   Shutdown [normal|transactional|immediate|abort]
•   Normal - disallow new user to connect, unless disconnect first myself
•   Transactional - disallow new user to connect, current user will disconnect once all transactions                            commited
•  Immediate - disallow new user to connect,rollback all transactions and then disconnect
•  Abort - forcely disconnect all user connections. if the 3 above don't work or hang there, use this!