(Integrity servers only) This parameter controls the usage of
    system service interception. SSI_ENABLE is turned on by default.

    System Service Interception is a mechanism that allows user
    specified code to run before, after or instead of the intercepted
    system service. This mechanism is available on OpenVMS Alpha
    Version 6.1 and later and OpenVMS Integrity servers Version
    8.3 and later, but the parameter SSI_ENABLE is relevant only
    on Integrity server systems.