SQL Server connection string Asynchronous Processing=true?

Just having the Asynchronous Processing=True in your connection string just simply enables you to write asynchronous queries - I don't see how having that setting in your connection string should affect your performance, if you don't change anything else.

Just having the Asynchronous Processing=True in your connection string just simply enables you to write asynchronous queries - I don't see how having that setting in your connection string should affect your performance, if you don't change anything else. You will hopefully begin to see a positive effect on your performance when you start doing asynchronous processing of your database queries. But just specifying that one option shouldn't have any (positive or negative) impact on your app.Marc.

Thanks Marc! 1. Does this option mean, if I enable this option, then I can use asynchronous API from ADO.Net, and if I disable this option, I cannot use asynchronous API from ADO.

Net? 2. If I am not using asynchronous API from ADO.

Net, I am not sure whether this option has any impact to my code if I do not use any asynchronous API from ADO.Net. I have this confusion because I am not sure whether underlying ADO.Net code use asynchronous processing to optimize performance (e.g. Using thread pool queue work item) -- so if I set false to this option will block underlying code from optimization? – George2 Oct 29 '09 at 16:25 2 as far as I understand it, this setting just enables you to use async ADO.NET queries - but it doesn't do anything automatically.

And yes - if you haven't specified this setting, you will NOT be able to use async ADO. NET queries. – marc_s Oct 29 '09 at 16:29 1 It enables async ADO.

NET queries - but unless you actually write such async queries, it has no effect. – marc_s Oct 29 '09 at 17:29 1 As marc_s mensioned enabling or disabling async processing have no impact at your sytem performance. Even if you write your code to use async queries, this queries would not perform faster than without async calls.

All it does is performing your query in another thread while your current thread remains responsive. – Tror Oct 29 '09 at 20:59 1 @Tror: good point - the query isn't really faster, but it "feels" faster to the user – marc_s Oct 29 '09 at 21:22.

Contradictory to what the accepted answer says, it actually has an impact on performance. Atleast: according to the msdn documentation. In practice however I wasn't able to see any difference in a SQL 2005 Express scenario with .

Net 3.5 SP1. Since MSDN docs warns about this I thought it should be interesting for future reference.

As a matter of fact, there are performance issues when you enable that option; see the ADO. NET 2.0 Asynchronous Command Execution (ASYNC) FAQ: Q: What is the new ADO. NET 2.0 Asynchronous Command Execution feature.

A: ASYNC allows you to execute a command in a non-blocking manner. We are exposing in the SqlCommand the following asynchronous methods: BeginExecuteNonQuery, BeginExecuteReader and BeginExecuteXmlReader with polling, synchronization and (shudder) callbacks. ... Q: So does this mean that every command I execute (sync or async) will happen in overlapped mode when I add ASYNC=TRUE to the connection string?

A: Yes it does, everything that we execute on this connection will be done in overlapped mode. For synchronous operations we internally wait for the completion before returning, we are basically faking the synchronous behavior on this connection. This is the reason why we require a connection string keyword.

Q: Does this have a perf impact? A: Definitely, only use ASYNC=TRUE when you know that you are going to be using the async functionality. ...

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