Examining SQL Server sessions

I recently needed to see the number of SQL Server sessions connected to a database, and what they were doing.

There are these handy stored procedures to list the current (and currently executing) sessions in a SQL Server database.

sp_who: Comes pre-installed. Lists session currently connected to a database. More info here.

But typically people prefer sp_who2, which displays more information.

sp_who2: Comes pre-installed. Lists session currently connected to a database. More info here.

But to easily see the active sessions, and what they're currently doing, you want sp_who3.

sp_who3: You need to install this yourself.  (Definition is here.) Lists only sessions with a currently executing request, along with what that SQL statement is.

ASP.NET limits the number of form variables

Did your form post suddenly stop working?

On Dec. 29, 2011, Microsoft released a security fix through Windows Update (MS11-100). Among other things, this fix limits the maximum number of form variables, files, and JSON members in an HTTP request to 1000.

As described in http://support.microsoft.com/kb/2661403, HTTP clients that make these kinds of large requests will be denied, and an error message will appear in the web browser. The error message will usually have an HTTP 500 status code.

But the catch is, the only true indication that you're encountering this problem is the specific exception stack trace visible in the event log (or in the rendered ASP.NET page, if your web.config <customErrors mode="..."> allows it).  An example:

[InvalidOperationException: Operation is not valid due to the current state of the object.]
   System.Web.HttpRequest.FillInFormCollection() +468
   System.Web.HttpRequest.get_Form() +79
   System.Web.HttpRequest.get_HasForm() +73
   System.Web.UI.Page.GetCollectionBasedOnMethod(Boolean dontReturnNull) +54
   System.Web.UI.Page.DeterminePostBackMode() +90
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +268

This new Microsoft limit can be configured on a per-application basis in web.config. In the <appSettings> section, add a new key for "aspnet:MaxHttpCollectionKeys" with an appropriately large value for your specific site:

 <add key="aspnet:MaxHttpCollectionKeys" value="2000" />

There is a separate limit for JSON members:

 <add key="aspnet:MaxJsonDeserializerMembers" value="2000" />

Note: If you are using ASP.NET 1.1, the setting is adjusted by adding a DWORD value to registry keys; see http://support.microsoft.com/kb/2661403.