Memory Leak: MS-DOS-Based Apps Starting Non-MS-DOS-Based Apps

Last reviewed: September 14, 1995
Article ID: Q128550

The information in this article applies to:

Microsoft Windows NT Workstation version 3.5
Microsoft Windows NT Server version 3.5

SYMPTOMS

MS-DOS-based applications that start Windows-based, POSIX, or OS/2-based applications under Windows NT may experience memory leaks.

CAUSE

Two different memory leaks can occur. One memory leak occurs when the MS- DOS-based application does not close a Process Object handle properly.

To observe the memory leak:

Run Performance Monitor.
From the Edit menu, choose Add to Chart.
From the Object list box, select Objects.
From the Counter list box, select Processes.
Choose Add and then choose Done.

A leakage of this resource will result in the gradual depletion of non- paged pool (a vital Windows NT resource).

The other memory leak occurs when an MS-DOS-based application continuously starts non-MS-DOS-based applications, creating a looping situation. This results in the loss of Private Bytes associated with NTVDM.EXE running the MS-DOS-based application.

To observe the memory leak:

Run Performance Monitor.
From the Edit menu, choose Add to Chart.
From the Object list box, select Process.
From the Instances list box, select NTVDM.
From the Counter list box, select Private Bytes.
Choose Add and then choose Done.

It may be difficult to log if there are multiple instances of NTVDM running, as Performance Monitor will not let you distinguish between these instances if they share the same executable name. (The Windows NT Resource Kit describes methods to overcome this situation.) A leakage of this resource results in the gradual consumption of Private Bytes for the NTVDM.EXE process. Private bytes consumption is general backed by paging file so a leak of Private Bytes will slowly consume the pagefile (a vital Windows NT resource).

STATUS

Microsoft has confirmed this to be a problem in Windows NT version 3.5. This problem has been corrected in the latest U.S. Service Pack for Windows NT version 3.5. For information on obtaining the Service Pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

   S E R V P A C K

KBCategory: kbother
KBSubcategory: nt16ap ntdosap ntos2ap ntposixap
Additional reference words: prodnt 3.50 handles batchfile page file

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Last reviewed: September 14, 1995
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