Keeping in mind that the number of connections is auto-expanding, and also my other notes from your previous post/question, if you approach or surpass the efficiency zone (500-700 active connections per listener), responsiveness to user requests will seem to be slow although once a request is picked up the response should be quick as usual.
The keyword here is "active" connections. If you have 9000 users connected but only 300 of them are actively submitting requests (new queries or even just "next block of data" requests) then you will still be OK.
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Art S. Kagel, President and Principal Consultant
ASK Database Management Corp.
www.askdbmgt.com------------------------------