Solved|| Error: 503 - Service Unavailable @https://community.oracle.com/message/13168925#13168925
This is the root cause of your issue. The apex pool in ORDS corresponds to the database APEX_PUBLIC_USER and it is not correctly configured. Connect to the SQL Plus prompt with SYS user and SYSDBA privileges and run the following query: // select username , account_status , profile from dba_users where username in ('APEX_PUBLIC_USER','APEX_LISTENER','APEX_REST_PUBLIC_USER'); If the account status is LOCKED, EXPIRED, etc then unlock the user accounts for example: // ALTER USER APEX_PUBLIC_USER IDENTIFIED BY <password> ACCOUNT UNLOCK; Discard/delete the current ORDS configuration and re-configure ords.war/apex.war with correct passwords for the users. Re-deploy it to Glassfish Server.