Oracle DBMS Scheduler Email Notifications Dynamically Send Server and Instance Name
SYS_CONTEXT can be used to extract the host name of the database server and the instance name.  

You simply call dbms_scheduler.add_job_email_notification in order to add the email notification like the following:

BEGIN
DBMS_SCHEDULER.add_job_email_notification (
  job_name =&gt; &lt;JOBNAME&gt;,
  recipients =&gt; &lt;EMAIL&gt;,
  subject =&gt; 
    SYS_CONTEXT('USERENV','SERVER_HOST') || ' ' || 
    SYS_CONTEXT('USERENV','INSTANCE_NAME') ||
    ' - Scheduler Job Notification-%job_owner%.%job_name%-%event_type%', 
  events =&gt; 'job_failed');
END;


The 12c documention for all of the SYS_CONTEXT parameters can be found here.