Topic overhead

Hi,
This is my first foray into JMS so please bear with me. I am trying to
transfer messages using publish / subscribe, and I have two distinct
types of message to transfer. I was wondering if it was appropriate to
use two different  administrated topic objects to transport each of
the different types?

What's the semantic level at which it's generally accepted that
messages should be going over a new channel?

Does using two topics instead of one have any impact on performance?

Many Thanks
Tom

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