SSIO_SYNC_INTVL is an OpenVMS system parameter. It defaults to "30", can be set to a miminum of "5" and a maximum
of "65535". The unit is measured in seconds.

This is probably zero help to you as you already know this from system output. As of Oct 28, 2007, there are no
matches in google.com or search.hp.com (with the "HP OpenVMS systems" option checked. How can an operating system 
parameter have absolutely no documented references by the vendor or users? Soon, this will be the first and
only reference on the entire Internet to this clearly important system parameter.