Message Oracle PCC-02104 - Unable to connect to Oracle

ERRORUnable to connect to Oracle
CAUSEThe precompiler could not connect to Oracle with the username, password, and, if applicable, database link that was supplied. Note that this is a precompiler message, not a runtime message. This means that the USERID option value, either on the command line or in a configuration file, was incorrect.
ACTIONCheck that the username and password are current and correct. Run SQL*DBA or SQL*PLUS and verify that connection can be made using that username and password.