HOWTO: Reducing RAM Memory to Test Visual FoxPro Applications

• Microsoft Visual FoxPro for Windows, version 3.0

SUMMARY

In previous versions of FoxPro, you could limit the amount of memory available to FoxPro by including a MEMLIMIT statement in the FoxPro configuration file. Visual FoxPro no longer uses the MEMLIMIT statement. Visual FoxPro dynamically allocates memory as it is needed; therefore the total amount of memory that Visual FoxPro is using varies at any given time.

When testing a Visual FoxPro application, you may need to test the application on systems that have varying amounts of memory. This is particularly important when determining the system requirements (memory requirements) for a Visual FoxPro application. The only way to limit the amount of memory available to Visual FoxPro is to limit the amount of memory available to the operating system, so the method used to limit the memory available to Visual FoxPro will vary depending on the operating system.

MORE INFORMATION

Windows NT

To limit the amount of memory available to Visual FoxPro running under Windows NT, you need to edit the Boot.ini file. The Boot.ini file specifies start up options for Windows NT. It is located in the root directory of the boot drive. The /MAXMEM switch is an undocumented switch that allows you to specify the maximum amount of RAM memory that Windows NT will use. This switch is placed at the end of the ARC path in the [Operating System] section of the Boot.ini file. The following example forces Windows NT to use only 10 MB of RAM:

   multi(0)disk(0)rdisk(0)partition(1)\winnt= Windows NT /MAXMEM=10

Windows 95, Windows 3.x, and Windows for Workgroups 3.x

These operating systems do not provide a way to limit the amount of memory available. To limit the amount of memory available to these operating systems, you must allocate extended memory to something else to make it unavailable to the operating system. The easiest way to do this is to set up a RAM drive. A RAM drive uses the computer's RAM memory to simulate a disk drive. Once this memory is allocated to the RAM drive, it is unavailable to any other part of the operating system, including Visual FoxPro. A RAM drive is created by loading the Ramdrive.sys device driver in the Config.sys file. If the system had 16 MB of RAM, and you want to limit the amount of available memory to 10 MB, create a 6 MB Ram drive. Adding the following line to the Config.sys file will create a 6 MB RAM drive:

   DEVICE=C:\WINDOWS\RAMDRIVE.SYS 6144 /E