In order to provide the highest possible level of compatibility with DOS applications which make use of particular DOS properties or attributes, MVDM provides virtual DOS machines with many more customizable properties than comparable OS/2 sessions. MVDM provides a common mechanism which supports standard settings, and allows virtual device drivers to register custom settings. The CONFIG.SYS file contains a number of standard DOS settings; these are applied to all VDMs as they are created. Other settings may be specified for individual VDMs.
When running Windows applications in VDMs under OS/2 Version 2.0, certain DOS settings should be altered from their default values. The recommended values for these settings when running Windows applications are discussed in DOS and WIN-OS/2 Settings.
DOS settings are used during creation and initialization of a VDM, and certain settings may also be altered dynamically during VDM execution. During initialization of the VDM, the VDM_CREATE hooks for all virtual device drivers defined for that VDM are called by the Virtual DOS Machine Manager. At this point, the virtual device drivers may call the VDHQueryProperty() helper service to get the values for required settings.