The Sniffer in the Stream Viewer can be used to create a "log" file of all the request and responses being sent and received from the product. However, this file is not as structured as the Stream Viewer itself so it's not that straight forward to easily find what you are looking for.

If you are specifically interested in the amount of traffic or specific data (OIDs in this case) being requested, then you will probably be better creating a WireShark capture to get all communication from DataMiner to the product and vice versa. This will also make it easier to filter on specific OIDs for example.

There is no easy answer to your question related to what amount of traffic is normal/too much. This will depend on numerous factors such as the amount of requests the snmp agent of the product can handle, the bandwidth of the connection between DataMiner and the product, etc. In most situations, retrieving the data is done via timers (for example every minute/hour/...) and we always make sure that the interval of our timer is not lower than the time it takes to retrieve the data from the product.

Hope this helps answer some of your questions.