SYSDBA password in Oracle DB I am connecting to Oracle DB using sysdba:

sqlplus / as sysdba


What is the default password for sysdba user. I tried in net and found out the default password is change_on_install but it is not working for me.

I am interested to know if Oracle DB maintains some file or DB table where it stores the passwords.
SYSDBA is not a user, it is a system privilege. When you connect as / you are connecting to the SYS user. You don't need a password when you connect as you are - as long as it's a local connection from an OS account in the DBA group.

You haven't said what happens when you try to connect, or why you think you need a password; possibly that is that failing (in which case giving the error message would be helpful) and giving you a SQL*Plus login prompt, maybe indicating you aren't in that group.

Passwords are stored within the DB, the exact location depends on version; but they're stored hashed (of course) so you're not going to be able to get the actual passwords in plaintext (without a lot of time and effort anyway).