<p>I am looking for any tool which will allow the performance testing/tuning of Sybase nested stored procedures. There are many tools around and of course Sybase's own for performance tuning and testing SQL but none of these can handle nested stored procedures (i.e. a stored proc calling another stored proc). Does anyone have/know of such a tool?</p>

There are some things you can do with web.config like defining security settings etc...
Other times you have to use HttpModules or HttpHandlers, look here:
http://msdn.microsoft.com/en-us/library/aa719858(VS.71).aspx
If not, you can find different ISAPI, but in this case you need access to IIS.
For example, the ISAPI for emulating rewrite mod apache:
> http://www.codeplex.com/IIRF
The other question, yes ASPNETDB.MDF in APP_Data is protected normally (it depends on your administrator). To change the path, change the connectionstring.