I have a dll which invokes sqlldr (oracle) to insert data from flat file to Oracle DB. When I access it from ASP code with parameters like control file name and all nothing happens but if I pass no parameters then the SQLLDR.EXE is shown in the Task Mgr. Anyone faced such issues ?

could be a permissions issue with IIS. It may not have the rights to open the ctl file for sqlldr. Try checking this...

Also, unless the ctl file has inline data, you should also check IIS user has permissions to the data files your ctl file is trying to load.