Hi,
Thanks for the reply. Support have answer the actual question and even if you are allowed to install the MIB on the server it is not supported to add any OPTS param to the SSG jvm to make it accessible for the SNMP server.
On the other hand, they provide me with a JvmMetricsAssertion SJAR tool kit that I was able to install in the Policy Manager and now I have all the required metrics that I needed from the gateway. It make use of the Tactical Agent to generate thoses data if I understand correctly what they said to me.
I will began to let go of SNMP as of now, also knowing that in JDK10, there is no support of SNMP anymore as it was depreciated by Oracle :https://www.oracle.com/technetwork/java/javase/10-relnote-issues-4108729.html
Thanks again for your help !