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Figure 5-2: Restaurant running under shared waitress mode. It is similar
as Oracle Instance running under Shared Server Mode.
One more thing that I like to mention here, in a restaurant
environment, if it's really busy, then you may have to wait
unless someone leaves and you get the place to sit. So there will
be a “waiting list” maintained by someone, as soon as you enter
the restaurant that person will note down your name in the list
and whenever there is a vacant place to sit and provided its your
turn on the list, you will be directed to that vacant place.
Similarly in Shared Server mode there is a dispatcher process,
which receives the users requests and places it in the “Request
Queue”. Server process “when it's free”' picks up the request
from the request queue, processes it and put the response back in
response queue. Dispatcher process “when it's free” picks up the
response from the response queue and sends it to the specific
user who submitted that request.
The point to be noted over here is that request and response
queues are not processes.
They are part of SGA or in other words
part of memory utilized by processes. Whereas Server process
and Dispatcher process are processes and are not the part of
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