I might be missing something, but is there a reason to run the XML extract as a subquery?

You have something like:

insert into table (...) select ... from (select ... from...

Not specifically AJAX related, but I saw some similar issues with our application.

I think the core of the problem is that the microsoft XML document manipulation routines are relatively slow....

You can't create a variable in the batch and have it be accessible in the dynamically executed SQL. The variable has to be part of the dynamic SQL.

When you run...

I've run into this same problem many times, myself.

Remember: the plan that gets cached is the result of the first call to the stored proc. In our system, we have...

A few issues I see with this approach. I'm curious as to your opinion on them:

1) It does nothing to prevent SQL injection attacks. I can pass in something like...

Ran into a very similar problem here. Since you have the correct indexes, try using:

SELECT distinct Prcs_dte

FROM tbl_Tracking

WHERE NOT EXISTS (Select prcs_dte FROM Acct_Stats where prcs_dte = tbl_Tracking.Prcs_dtr)

I made...