SMS: Dos4gw.exe Causes Memory Inventory Inaccuracy

• Microsoft Systems Management Server, versions 1.0 and 1.1

SYMPTOMS

MS-DOS clients that run the DOS extender Dos4gw.exe before Systems Management Server hardware inventory is collected may result in unlikely extended memory values in client inventory. For example, an MS-DOS client with 32 MB of memory that runs Dos4gw.exe in the Autoexec.bat (before hardware inventory is collected) may report 64 MB of extended memory in client inventory.

CAUSE

Memory inventory is incorrect because Dos4gw.exe is not closing high memory area (HMA) handles it uses to access XMS memory. Dos4gw.exe opens HMA handles to access XMS memory managed by the resident A20 handler (such as Himem.sys).

Systems Management Server memory inventory is collected by summing the total amount of memory in use by the available HMA memory handles. In this case, Dos4gw.exe is not closing some HMA handles when it quits, leaving two handles still allocated. In the 32 MB client example Dos4gw.exe opens a handle for 516K, and another for 30,440K. When Dos4gw.exe exits, it does not close its HMA handles; when Systems Management Server inventory sums them with the default handles in use (totaling 31,680K), the extended memory value is reported incorrectly as 62,636K.

WORKAROUND

To work around this problem, run Dos4gw.exe after the Systems Management Server hardware inventory has been collected.

STATUS

The products included here are manufactured by vendors independent of Microsoft; we make no warranty, implied or otherwise, regarding these products' performance or reliability.

MORE INFORMATION

The following table is the combined results of a test application, showing Dos4gw.exe failing to close HMA handles 11 and 12 after closing:

Before Dos4gw     After Dos4gw

Handle  0 = 344   Handle 0 = 344
Handle  1 = 1     Handle 1 = 1
Handle  2 = 8     Handle 2 = 8
Handle  3 = 7     Handle 3 = 7
Handle  4 = 10    Handle 4 = 10
Handle  5 = 5     Handle 5 = 5
Handle  6 = 6     Handle 6 = 6
Handle  7 = 12    Handle 7 = 12
Handle  8 = 6     Handle 8 = 6
Handle  9 = 65    Handle 9 = 65

Handle 11 = 0     Handle 11 = 516
Handle 12 = 0     Handle 12 = 30440
Handle 13 = 0     Handle 13 = 0
Handle 14 = 0     Handle 14 = 0
Handle 15 = 0     Handle 15 = 0
Handle 16 = 0     Handle 16 = 0
Handle 17 = 0     Handle 17 = 0
Handle 18 = 0     Handle 18 = 0
Handle 19 = 0     Handle 19 = 0
Handle 20 = 0     Handle 20 = 0
Handle 21 = 0     Handle 21 = 0
Handle 22 = 0     Handle 22 = 0
Handle 23 = 0     Handle 23 = 0
Handle 24 = 0     Handle 24 = 0
Handle 25 = 0     Handle 25 = 0
Handle 26 = 0     Handle 26 = 0
Handle 27 = 0     Handle 27 = 0
Handle 28 = 0     Handle 28 = 0
Handle 29 = 0     Handle 29 = 0
Handle 30 = 0     Handle 30 = 0
Handle 31 = 0     Handle 31 = 0
Total     = 31680 Total     = 62636