> What are the possible reason for a SP that normally runs in approx 20 seconds
> then Occasionally takes 15 minutes, (or a method of trying to find the cause of
> the problem).
>
>
>
> Firebird Details
> Server Version: WI-V2.5.5.26952 Firebird 2.5 32 bit Superserver,
> CpuAffinityMask = 1 in firebird.conf

A few ideas:
* Some sort of lock contention at transaction level caused by concurrent read/write requests on the same (range) of records running transaction in WAIT and/or NO RECORD_VERSION mode
* Firebird 2.5 Superserver is basically single CPU/core bound for a single database environment, but IMHO not an explanation for that large difference
* Watch out typical response time influencers like execution plan, I/O fetches, records fetched etc ...
* Query the monitoring tables when your SP is stalled and/or run a continuous trace through the Trace API



--
With regards,
Thomas Steinmaurer
http://www.upscene.com

Professional Tools and Services for Firebird
FB TraceManager, IB LogManager, Database Health Check, Tuning etc.