A JSwat Session is the object that manages the debuggee VM. It launches a debuggee or connects to a remote debuggee. A Session can suspend and resume the debuggee. The Session also keeps a variety of persistent settings called properties.
The properties of a Session include the classpath, sourcepath, list of single-step exclusions, last-used search phrase, watchpoints, main debuggee class, remote host and port, JVM options and so on. All of these properties are initially empty until they are defined during normal interaction with JSwat. The properties are automatically saved to persistent storage for subsequent reuse.
JSwat has support for multiple sets of Session properties. Only one set can be loaded at any given time. The "File" menu has items for opening, copying, and deleting sessions. By default there is a session with the name "default". You can delete this and it will be remade with empty properties.
At startup the session is inactive. This is discernible by the fact that numerous menu items and toolbar buttons are disabled during an inactive session (such as the single-step buttons). To activate the session, click the "New" icon on the toolbar or select "Start VM" from the "VM" menu. Once the session has activated, the full set of menu items and toolbar buttons becomes enabled and ready for use.