At 10:08 AM 2/23/2001 +0100, Lutz Kutscher wrote:

>The main application working on our Database is a cash register software.
>Up to 25 cash registers are connected to the Database. All
>requests/queries from
>these should always have priority over any request/query from any other
>workstation
>in our network (e.g. statstics query, price changes etc).
>
>So now to my question:
>is it possible to set the priority, in which a query is processed depending on
>the user login?

No. InterBase's concurrency control is vastly different from Sybase and
(in my biased view) much more satisfactory. Readers never block writers
and inserts never conflict unless they violate a uniqueness constraint.
Before you decide not to use InterBase because it doesn't let you control
priority, try it. You may be surprised.

>If this option does not exist, are there any chances of it being
>implemented in some future version of Firebird?

Nothing is impossible, but this is not a feature I would encourage.

First, because I think it's unnecessary. Yes, occasionally one
query will hog the processor and that's a bad thing. We'll work
on the threading issues to fix that. Yes, a runaway query can
waste a lot of time. We'll work on tools that find and stop runaway
queries.

Second, because it could degrade performance for both high and low
priority processes. InterBase depends heavily on the ability of
a process to request a resource and get it quickly. That in turn,
requires that a process holding a resource be able to release it
quickly. It is easy to imagine a high priority process needing a
page while blocking the lower priority process that has the page
but can't get a quantum to release it. [Reminds me slightly of my
cat, trying to get under the covers while standing on them.]


Regards,

Ann
www.ibphoenix.com
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