MVDM provides the user with the ability to customize the operation of DOS applications via a feature called DOS Settings. This feature allows the user to control special properties which affect the behavior of DOS applications running in a VDM.
The DOS Settings feature further enhances the DOS compatibility of a VDM because it allows a user to configure the VDM for DOS applications which might otherwise not work well (or not work at all) with the default settings for a VDM. The DOS Settings feature also gives the user more control over the consumption of system resources by a DOS application. Help is provided for each setting to assist users in tuning their applications' operation.
DOS sessions have many more customizable properties than OS/2 sessions. MVDM provides a common mechanism that supports both a standard complement of settings, and allows virtual device drivers to register custom settings. The standard settings are a subset of the configuration settings available in the CONFIG.SYS file, plus some additional settings required for MVDM. The primary reason for the existence of the option to alter these settings is that DOS applications are typically not careful about consuming system resources, such as memory and processor time. Hence, MVDM itself must provide a flexible environment for these applications in order to preserve the integrity and performance of the system as a whole.
DOS settings are managed on a per-VDM basis and are accessed through Presentation Manager windows. The dialog boxes presented allow the user to change a setting while the VDM is running. Only those settings that can be changed for that VDM are presented. There are many settings which can be tuned. One parameter, for example, the Idle Detection Threshold, detects idle DOS applications and allows the user to configure the system such that processor time is not wasted by idle DOS applications.
Note that while the DOS Settings feature provides significantly enhanced control over the behavior and capabilities of a virtual DOS machine, this level of control is not necessarily obvious to the end user. Most DOS applications will execute quite satisfactorily with the default VDM settings, and the user is therefore not required to use the DOS Settings feature. This approach therefore provides the increased functionality without necessarily increasing the complexity of user interaction.