Programs (16-bit .exe) May Start NTVDM at 100% CPU Utilization

ID: Q176965

The information in this article applies to:

Microsoft Windows NT Workstation version 4.0
Microsoft Windows NT Server version 4.0
Microsoft Internet Information Server version 1.0, 2.0, and 3.0

SYMPTOMS

Internet Information Server (IIS) does not support Web links that launch 16- bit applications as CGI scripts. This article details a particular problem that occurs as a result of IIS not supporting such Web links. It also explains why the problem occurs. A symptom of the problem is a slow server showing Task Manager with one session of Windows NT Virtual DOS Machine (NTVDM) running at 100 percent of CPU utilization.

MORE INFORMATION

At least one session of NTVDM is always associated with a launching of a 16- bit application. Internet Information Server launches a Web page link to a 16-bit application as a CGI script. In this case, the process is spawned by IIS to run in a non-interactive state, with spawn parameters that do not permit the application to receive console-user input. In the case where a 16-bit application requests console-user input and polls the keyboard for input, especially in a tight loop, CPU utilization may increase to 100 percent.

This problem may occur in some large Web sites where the following two things are unclear:

1. That the same Web link points to a 16-bit application.

2. That the 16-bit application contains prompts for user input.

This issue becomes more problematic on large Web sites, where it is difficult to determine who spawned the executable. Task Manager, which you access by double-clicking Taskbar, only details the name NTVDM, instead of the 16-bit executable name. To find the executable name, it is helpful to reference an IIS generated logfile, which is contained under the \winnt\system32\LogFile directory. This date-specific file contains a history of processes spawned by IIS by application name.

Here is an example of the logfile contents:

   C:\WINNT\system32\LOGFILES>type in971021.log
   107.57.227.160, -, 10/21/97, 17:11:48, W3SVC, COMPUTER1, 107.57.227.160,
   681, 437, 72, 304, 0, GET, /test2.htm, -,
   107.57.227.160, -, 10/21/97, 17:11:49, W3SVC, COMPUTER1, 107.57.227.160,
   141, 429, 72, 304, 0, GET, /samples/images/backgrnd.gif, -,
   107.57.227.160, -, 10/21/97, 17:26:51, W3SVC, COMPUTER1, 107.57.227.160,
   900334, 423, 275, 502, 0, GET, /scripts/test2.exe, -,

Viewing this logfile output should make it easier to track down the name of the 16-bit spawned executables. Since spawning 16-bit executables from Web links is not supported under IIS, it is a good idea to review all executable files under the IIS directories.

16-bit executables show the following tabs under Windows Explorer/Properties:

   General, Program, Font, Memory, Screen, Misc
   (Example: Go to Windows Explorer and find \winnt\system32\edit.com.
   Right click and choose Properties).

32-bit executables show only the following tabs under Windows Explorer/Properties:

   General, Version

Additional query words: 4.00 prodiis 16Bit vdm dos app dosapp Zip file zip files processor util

Keywords          : kbinterop NTInterop nt16ap nt32ap NTSrvWkst 
Version           : WinNT:4.0
Platform          : winnt
Issue type        : kbprb
Solution Type     : kbnofix

Last Reviewed: April 22, 1998