When you log in on the SE Manager, a session with a unique session ID is set up. The server regards all requests with the same session ID as connected and they are assigned to your account. The SE Manager displays an overview over the active sessions under Authorizations -> Users -> Sessions (see section "Displaying sessions").
This means in particular that a session which has not yet timed out is regarded as still valid when, in the browser, you close the tab via which you are logged in on the SE Manager (without logging out explicitly). When you connect to the SE Manager again before the session timeout has expired, you are redirected again to the main window opened most recently without having to log in once more.
Local and global sessions
SE Manager sessions are global under the following conditions:
The MUs are integrated into an external DNS in the same network domain.
The SE Manager is called via the DNS name of the MU (entering the FQDN) and not via the IP address.
A global session is a cross-MU session. This means that in SE server configurations with more than one MU (MU redundancy or Management Cluster), you only have to log in at the SE Manager of one MU. After that, you can switch from the SE Manager of the local MU to the SE Manager of another MU without having to log in again.
The same is true for add-on applications, i.e. you can operate the add-on applications on a different MU from the local SE Manager.
A local session is MU local. It is only created if you address an MU via the IP address during login. The name of the MU for which the session is valid, is displayed. You must log in again when you switch to another MU.