ORA-20000

I got the error:

EXTERNAL_LOG_ID="job_173118_9",
USERNAME="DB_HOST\user_agent",
STANDARD_ERROR="Launching external job failed: Invalid username or password"

Cause: On Windows, the host user that runs the external executable must be assigned the Log on as a batch job logon right.
http://docs.oracle.com/cd/B28359_01/server.111/b28310/scheduse002.htm#ADMIN12397

Action:  In the Control Panel, open Administrative Tools, then Local Security Policy.  Beneath Security Settings, open Local Policies and highlight User Rights Assignment.  Locate Log on as a batch job. Open the properties and add any users that need this right.  When finished, save your changes and close the Local Security Settings window.