Virtual device drivers used by DOS sessions take little or no memory below the 640KB limit. A user can install device drivers that are required by, and specific to, certain applications that run in a DOS session. If the commands to load these device drivers or other memory resident programs are added to the CONFIG.SYS file, these device drivers (or programs) are loaded into any DOS session. This reduces the amount of conventional memory available to DOS applications.
DOS settings allow a user to customize a DOS session. To ensure that the maximum amount of memory is available in each DOS session, load the necessary DOS device drivers for the DOS application by using DOS settings. For example:
It also is necessary to include a VXMS.SYS statement in the CONFIG.SYS file to have upper memory blocks available.
Eliminate DEVICE= statements for DOS device drivers from the CONFIG.SYS file unless the device driver is required for any DOS session.