Subscriber monitoring policies are applied per subscriber. They just determine the amount of sampling of DPI records for each subscriber. By default, the BQN comes with a monitor-default policy that applies to all subscribers, which automatically determines the number of DPI records (called UDRs, or Usage Data Records) to produce, so that the DPI statistics are meaningful and do not take too much CPU and disk to produce, and that is the recommended mode of operation:

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It is possible to adjust the amount of UDRs for certain subscribers by creating a monitoring policy that specifies percentage of flows with UDRs (e.g. 0% or 100%). UDRs for 100% of flows will produce and accurate description of the subscriber usage statistics, but for performance reasons, it is recommended to set a 100% UDR monitoring policies only on a few subscribers at a time, because these policies can produce a huge number of records that could use all the available disk space and could also make the production of DPI statistics very slow and CPU-consuming.

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