ucon/rfc/active is a SAP Parameter attribute which is used to control Activate RFC Service Runtime Checks information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
When the profile parameter UCON/RFC/ACTIVE is set to a vlaue greater
than zero, the incoming RFC requests will be additionally checked to
gurantee the security policy for calling of RFC enabled function modules
in ABAP system in accordance to the setting in phase tool (see xxx)
See SAP Parameter Documentation for full SAP documentation for this profile parameter.