Use the following steps, if someone is locking an oracle database user by entering wrong password.
Wrong password attemp limit is determined by FAILED_LOGIN_ATTEMPTS profile parameter.
So check it first. In our case we assume that it's value is 3.
ORA-01017: invalid username/password; logon dedied
ORA-01017: invalid username/password; logon dedied
ORA-01017: invalid username/password; logon dedied
ORA-28000: the account is locked