How does system fill MIB entries with Read-Only Access?
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For managing the system configuration, we use MIB Management Systems in some form or the other, which may be C-structure based or Yang Module for data modeling. Now there are entries in the MIB which are marked as read-only, or not accessible for the manager i.e. Northbound Interfaces. The operational data is often kept in such entries, like system up-time etc. 

So, is the filling of data by the Device itself in these fields implementation specific or does the device also use GET/SET/TEST type of mechanism to write to these MIB leafs?