When any updates are applied to the proxy servers, the apache service on that device is restarted causing existing httpd processes on the Access Gateway to be killed.
Although the impact to users is minimal, Apache does provide a graceful restart option that causes the parent process to advise the children to exit after their current request (or to exit immediately if they're not serving anything). The parent re-reads its configuration files and re-opens its log files. As each child dies off the parent replaces it with a child from the new generation of the configuration, which begins serving new requests immediately (http://httpd.apache.org/docs/2.2/stopping.html).
The Access Gateway (AG) implemented this graceful restart with 3.2 SP1 IR1, but it created a side effect ie. any policy updates on the AG would not get implemented until tomcat was manually restarted. This resulting issue caused the release of 3.2 SP1 IR1a which removed the original graceful restart feature that IR1 had.
Graceful restarts are now fully implemented in 3.2 SP2, where there is no need to restart the tomcat services after applying policy updates.