sys.database_usage.quantity = 1.8?

Question

I have 1 database in 1 server in 1 subscription. I don't create and drop databases on-the-fly (actually, at all). The documentation of the 'quantity' column of sys.database_usage says "The maximum number of databases of an SKU type that existed during that day". Not average number! Maximum. How can it be non-integer?

SELECT * FROM sys.database_usage

time        sku    quantity
...
2012-05-22  Web   1.8
2012-05-23  Web   1.8
2012-05-24  Web   1.8

Why is 'quantity' a non-integer number?

In fact, I have been billed for 1.7936 "database units" during the last month, while in fact I always had exactly 1 database (of changing size 2GB - 3.5GB). I can see that the average of the numbers in sys.database_usage.quantity is around 1.7936 for the given period (actually 1.8533) because those numbers are 1.8, 1.4, 2.2, 2.6 -- never an integer.

Can somebody explain it to me?

Another (related) question. The invoice contains two items: "Data Transfer Out (GB)" (it's ok) and "Database Units" (the above-mentioned 1.7936). How does the unit price ("Rate", £6.0549≈$9.99) reflect the Flat $9.99 for the first 1GB and $3.996 per GB? I think these should be two items in the invoice..

Answer 1

OK, I got it.

$3.996/$9.99 = 0.4

This is why I see 1+n*0.4 values in sys.database_usage.quantity. n is the number of GBs the database occupied above the first GB (= the base amount that is included in the flat price). If I had business edition with MAXSIZE > 10GB then quantity=1.0 would mean 10GB, and an actual size of 10+nGB would be seen as quantity = ($45.954 + n*$1.998)/$45.954 ≈ 1+n*0.04348.

Sorry for taking your time. (Nevertheless, it was useful because all existing documentation on this topic is far from being clear...)

Please post here a link to the official documentation that explains it, if you are aware of one...

Answer 2

Thank you for sharing experiences

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