Documentation Recommends Removing/Reducing Virtual Memory

ID: Q115182

The information in this article applies to:

Microsoft FoxPro for Windows, versions 2.5, 2.5a, 2.5b, 2.6
Microsoft FoxPro for Macintosh, versions 2.5b, 2.5c

SUMMARY

The FoxPro for Windows and FoxPro for Macintosh configuration manuals incorrectly recommend removing virtual memory if your system has more than 4 megabytes (MB) of random access memory (RAM). Furthermore, the FoxPro for Windows configuration manual incorrectly recommends creating a 2-MB swap file if your system has 4 MB of RAM.

Following these recommendations may prevent your system from running FoxPro or other applications due to insufficient memory.

In general, it is best to have as much virtual memory as required to run all of your applications, provided you have sufficient hard disk space to support that amount of virtual memory.

MORE INFORMATION

Virtual memory is free disk space that is used to simulate additional memory. When the system runs low on available physical RAM, it uses an algorithm to swap code and data from physical RAM to the hard disk.

The benefit of virtual memory support is that you can run more programs than can be supported by actual physical RAM. The drawbacks are the disk space requirement for the virtual memory swap file and a decrease in overall execution speed when swapping is required. However, it's generally better to be able to run a program slowly in a virtual memory system than not to be able to run it at all.

NOTE: Simply enabling virtual memory does not degrade system performance. Code and data are not swapped to the hard disk unless there is insufficient physical RAM.

For more information about using virtual memory and swap files in Windows, query on the following words in the Windows section of the Microsoft Knowledge Base:

windows and swap and file and virtual and memory

NOTE: In the FoxPro for Windows "Installation and Configuration" manual, the note at the bottom of page 3-3 says:

If you do need a swap file, make sure you create a permanent swap file rather than a temporary swap file.

This information is true for performance reasons only. However, if you need virtual memory but cannot use a permanent swap file because of system- compatibility problems or a lack of hard-disk space, you can use a temporary swap file instead.

Locations of Documentation Errors

FoxPro for Windows "Installation and Configuration," page 3-2:

For the best performance on a machine with 4 MB of RAM:
- Use a 2 MB permanent swap file for virtual memory.
- Do not use a swap file for virtual memory. Set your virtual memory to None.

FoxPro for Macintosh "Installation and Macintosh Features Guide," page 42:

For the best performance on a machine with more than 4 MB of RAM:
- Set virtual memory off.

Additional query words: FoxMac FoxWin 2.50 docerr


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