The G&R DSA listener (nl_dsa) is used to accept incoming connects to a
Host Links platform, usually to GUFT or Gspool configured to start-on-
demand. If the OCS (communications) server is taken down before taking 
down TDS on GCOS7 it does not terminate remote TCP/IP sessions, 
including DSA sessions running over TCP/IP (RFC1006). TDS is often taken
down this way to preserve user context. If the TDS application has opened
print sessions to start-on-demand instances of Gspool the sessions would 
remain open on the Gspool side. When TDS is restarted the print sessions 
are reopened, but for the Host Links Listener these looked like new 
connects, and so the Listener started a new instance of each Gspool. 
Eventually after several restarts of TDS the maximum number of incoming 
sessions supported by the Listener would be exceeded, resulting in reject 
of new sessions.

The listener now turns on KEEP-ALIVE on the RFC1006 port. The TCP/IP
stack on the Host Links platform now sends a keep-alive packet every
keep-alive interval (default 2 hours). If these are not answered the
session is aborted and the start-on-demand service terminates. Note
that a stop and then immediate restart of TDS will not be detected. New
instances of Gspool will be started, but the old instances will 
terminate when their keep-alive interval expires.

The workarounds depend on the situation. In the command line configured
for start-on-demand you can set the Gline parameter -ii nnn to
disconnect the session if it has been idle for nnn minutes.
Alternatively you need to stop and restart the Listener before taking
TDS up again. The stop/start of the Listener is always necessary if you
stop TDS and take it up again immediately, and want to avoid duplicate
instances of Gspool being started, with old ones living for the keep-
alive interval.