Each session - session or subsession - holds an ID.

• Session
  The ID of the session is unique inside one instance of Application Designer. If you have two Application Designer installations running, the same ID may be used inside both servers.

• Subsession
  The ID of a subsession is unique inside one session. If you have multiple sessions running inside one Application Designer instance, the same subsession ID may be used in two sessions.

You can access the IDs from your adapter in the following way:

public class TestAdapter 
    extends com.softwareag.cis.server.Adapter
{
    ...
    ...
    public void xxx()
    {
        ...
        String sessionId = this.m_interactionProcess.getSessionId();
        String subsessionId = this.m_interactionProcess.getProcessId();
        ...
    }
    ...
    ...
}