Azure SQL DW Concurrent queries by DWU and Resource class

Question

In "Concurrency slot consumption" section of https://docs.microsoft.com/en-us/azure/sql-data-WArehouse/sql-data-warehouse-develop-concurrency , It describes how the number of concurrent queries & concurrency slots varies by DWU and Resource Class. For "smallrc" resource class user, the number of concurrent queries and concurrency slots are 4 for 100 DWU and this number linearly scales upto 24 for 600 DWU (for 600 DWU, smallrc resource class user can run 24 concurrent queries on 24 concurrency slots).

My question is

1) How many concurrent queries can be run with all users running "smallrc" resource class on 1000 DWU ? As 1000 DWU provides 40 concurrency slots and each "smallrc" user takes 1 slot for running query, does it mean 40 concurrent queries can be run on 1000 DWU?? As per the documentation, it looks like maximum concurrent queries are 32. could someone please provide some details on this?

2) Also As per documentation, It looks like the max number of concurrent queries that can be run on SQL DW are 32 irrespective if i use 1000 DWU or 6000 DWU. could someone please provide details on why is this limitation ? if i use "smallrc" resource class user to submit queries on DW2000, are the concurrent queries still limited to 32 ?

Answer 1

1) From the documentation: "SQL Data Warehouse supports up to 32 concurrent queries on the larger DWU sizes." Having more concurrency slots only means that you can have more mediumrc and largerc queries running concurrently. For example on a DW1000 where the maximum slots are 40, smallrc takes 1 slot and mediumrc takes 8 slots, so you can have 4 mediumrc queries and 8 smallrc queries concurrently, or 31 smallrc and 1 mediumrc, but the max for total queries is still 32. You can still run some types of queries without using slots: https://docs.microsoft.com/en-us/azure/sql-data-WArehouse/sql-data-warehouse-develop-concurrency#query-exceptions-to-concurrency-limits

2) "The environment is intended to host DW workloads, which by their nature tend to be focused on running fewer, often more expensive, queries to return results that typically aggregate values over large datasets, vs an OLTP environment which is focused on running many concurrent, ideally very cheap, queries. By setting the limit to 32, the environment is designed to ensure that there are sufficient resources, especially memory, available for the expensive DW queries." - SimonFacer