We have an intermittent problem on one production server which leads to very slow response times for users. It happens 1-2 times per week so Black Box monitoring looked like a good place to start tracking down the cause.
Problem is that the 5Mb trace files filled every 2 minutes so by the time I got to hear about the slow response from the Help Desk, the data had already been over-written !
I've found that you can create larger trace files using the following SQL code
declare @TraceID int ,@fsize bigint, @fname nvarchar(128)
select @fsize=25, @fname=''
exec sp_trace_create @TraceID output, 8, @fname,@fsize
exec sp_trace_setstatus @traceID, 1
Trace files of 25 Mb gave me enough time to take copies the trace files for investigation at a later time.