Oracle 12c Username forgot - database

Question

a couple of days ago I installed oracle 12c. I ran it after a days or two but I completely lost my Username, I do remember my password but not username. I there any way by which I can see what username I set

Answer 1

Assuming that you can login as SYS, you can use:
select *
from dba_users
This will give all the users, including the one you defined; here you find something more.

Answer 2

There is new procedure for generating password since Oracle 11g. You can use
create or replace function get_hash_11g(p_password varchar2, p_salt varchar2) return varchar2 is
lv_pwd_raw RAW(128);
lv_enc_raw RAW(2048);
BEGIN
lv_pwd_raw := utl_raw.cast_to_raw(p_password) || hextoraw(p_salt);
lv_enc_raw := sys.dbms_crypto.hash(lv_pwd_raw, 3);
return lv_enc_raw;
end get_hash_11g;
/
Then run select
select w.name from sys.user$ w
where substr(w.spare4, 3, 40) = get_hash_11g(/*your password*/'&pass', substr(spare4, 43, 20));
/

Answer 3

Set up the following environment variables. They are not necessary for the process itself, but will help you navigate. In this case my domain is called "ClassicDomain". Remember to change the value to match your domain.
export MW_HOME=/u01/app/oracle/middleware
export DOMAIN_HOME=$MW_HOME/user_projects/domains/ClassicDomain
Shut down the WebLogic domain.
$ $DOMAIN_HOME/bin/stopWebLogic.sh
Rename the data folder.
$ mv $DOMAIN_HOME/servers/AdminServer/data $DOMAIN_HOME/servers/AdminServer/data-old
Reset the password using the following command. Remember to substitute the appropriate username and password.
$ cd $DOMAIN_HOME/security
$ java weblogic.security.utils.AdminAccount <username> <password> .

Answer 4

If you are able to invoke sqlplus then follow this:
sqlplus:/ as sysdba - this is the command needed to login as sys.
password: - don't give any password. Just hit enter
SQL> select username from dba_users; - this command will give list of users in the database.