Explanation:
JAVAUSEREDUCEDSIGNALS=1 notes.ini variable passes the -Xrs parameter to the JVM upon initialization, which applies to tasks that load JVM to run Java agents, such as HTTP or Amgr, and causes the JVM not to register signal handlers for SIGINT, SIGTERM, SIGHUP, and SIGQUIT. This parameter was introduced when HTTP was receiving a SIGINT from an unknown source, which would invoke the JVM's exit hook, and could cause crash of the Domino server.

Alternatively, the Domino server shouldn't be started in an SSH session (and then closing the SSH window), which then sends a SIGHUP (Hang up Signal) to all child processes, but in a remote shell instead, as documented in Technote #1085321.

Default:
This notes.ini setting is absent by default.

Recommendation:
This parameter should only be set on Unix and Solaris platform if the customer has a specific need or if recommended by Lotus support.

Restrictions:
This variable is only available on AIX, Linux and Solaris systems from Domino version 7.0.3, 8.0.1 and above.

Restarts:
The Domino server must be restarted after modifying this setting.

References:
Technote #1242500 - Domino server crashes when JVM receives a signal
Technote #1085321 - Exiting a Telnet Session Hangs a Domino Server on UNIX