Re: SQL and real time systems

On 8 Jan 2003 10:35:38 -0800, rogerbalakrishnan_at_hotmail.com (roger balakrishnan) wrote:

>hi,
>
>The rt system that I have been working on is actually a class 5
>telephone switch.
>We need to be able to support 64000 connections. Thus the connection
>table can have 64k entries.
>
>My problem with the design using sql that has been proposed is
>
>Consider if I have to get all the connections through a port card
>
>1) If I do a select statement it can return up to 64k items, I need to
>create a huge static block or allocate on the stack a block to get
>this data. That was my memory concern.
>
>2) I really only need to get records one at a time, so an interface
>getting a first, then allowing me to get a next and so on etc is
>better. Getting a single record can be done in log 64k accesses,
>getting the next in <= log64k accesses.
>(very snmp like).
>
>This is predictable wont use up memory and shouldnt take up a lot of
>processing time.
>
>The argument for using sql is that we can use a commercial database.
>
>I think it totally unsuitable.

Consider using a heap for storing your connection table in memory -- can be used like a binary tree or a priority queue -- space efficient -- but need to maintain auxiliary data structures if you need different access orders

Thanks. Take care, Brian Inglis Calgary, Alberta, Canada

-- 
Brian.Inglis_at_CSi.com 	(Brian dot Inglis at SystematicSw dot ab dot ca)
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