Along with these possibly new session identifiers, there has always been three session environment variables that get set from when a user connects to the database and are important when talking about tracing a particular session or group of sessions. These would be the SID, SERIAL#, and SERVICE_NAME. These have been around Oracle sessions for quite some time but are presented in Table 1 with the three new variables presented in Parts I & II of this series to provide for a quick refresher. This set of six session variables now gives us the ability to activate tracing for the session in a variety of ways.

Read more at: Oracle Session Tracing Part III