By definition, BHCA is the number of calls arriving in the busiest hour - it's not guaranteed, but the busiest hour is often the busiest day.
If you query the RCD and count the distinct RouterCallKey for each day and plot this, you can look back historically over the past year and find out which day had the highest number of inserts into the RCD. This is a very good estimate of the number of calls in that day. If you don't want to analyze further, and I would not bother really, you can use the industry figure of 20% - one fifth of the calls for the day occur in the busiest hour. This is conservative, but it's more than sufficient.
Because the RouterCallKey is reset each night, the easiest way to find the busiest day is to find the date which had the MAX value of the RouterCallKey. You have to be aware that you will get spurious results from this query if the Router was restarted that day, so discard those ones that are silly high.
This this the query
SELECT
RouterCallKeyDay
,CONVERT(NVARCHAR(30),DATEADD(dd,(RouterCallKeyDay-143905),'1995-01-01'),107) AS [Date]
,MAX(RouterCallKey) AS [MaxRCK]
FROM Route_Call_Detail
GROUP BY RouterCallKeyDay
ORDER BY [MaxRCK] DESC
So if we look at the results, you will see a couple of dates with really high values - but those are dates when the Router was restarted, so we discard them and focus on what looks like the top day.
August 10 is our selection. We can double check Aug 10 with
SELECT COUNT (DISTINCT RouterCallKey)
FROM Route_Call_Detail
WHERE DateTime > '2017-08-10' AND DateTime < '2017-08-11'
The result for that query is 226,204 which is pretty close to 226,452. I am pretty sure that the RCK starts at 300, not 1 each day so there is a bit of slop here. Anyway, the original query is close enough for government work.
So now we know the busiest day.
Estimate the busiest hour as 20% of that - around 45,000.
Regards,
Geoff
