Problems with Extended Memory

If an application in a VDM encounters an error due to insufficient extended memory, the following points should be checked:

  • Ensure the overall limit and the limit for the VDM are large enough to accommodate the amount of extended memory required by the application.

  • Ensure that the DEVICE= statement for VMXS.SYS is in CONFIG.SYS.

  • Ensure that the expanded memory driver VEMM.SYS, is not using all of the available memory. The amount of memory allocated to VEMM may be reduced by changing the parameters of the DEVICE= statement for VEMM to something less than that specified (or less than the default which is 4MB). If necessary, VEMM command may be disabled by removing or remarking out the DEVICE= statement in CONFIG.SYS.

  • Ensure that CONFIG.SYS and/or AUTOEXEC.BAT do not start unnecessary programs that use extended memory.

    If a program does not start and displays a message such as High Memory Area (HMA) already in use, the HMA may be freed by disabling the DOS=HIGH statement in CONFIG.SYS. If the statement is DOS=HIGH, UMB then the statement should be changed to DOS=UMB.


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