How to Distribute a Large Database with an Application

• Microsoft Visual FoxPro for Windows, versions 3.0, 5.0
• Microsoft FoxPro for Windows Distribution Kit, versions 2.5x, 2.6
• Microsoft FoxPro for MS-DOS Distribution Kit, versions 2.5x, 2.6
• Microsoft FoxPro for Macintosh Distribution Kit, versions 2.5b, 2.5c

SUMMARY

It is often desirable to ship large databases with applications. However, the Setup Wizard is not designed to split large files and may not be able to compress large database files, possibly resulting in the error message "Incorrect number of bytes written to disk - source file or destination disk may be corrupted - use ChkDsk."

To work around the size limitations of the Setup Wizard, you can use a number of third-party compression utilities, such as PKZIP, LHARC, StuffIt, and so on, to compress large database files. Many of these compression utilities are available on bulletin board services.

This article demonstrates how to use one of these utilities, PKZIP, to compress a large database so that it can be shipped with an application.

MORE INFORMATION

To ship a large database with your application, compress the database file, convert it to a self-extracting executable file, and then execute some code to expand (decompress) the compressed file.

For example, suppose you want to compress the files PICFILES.DBF and PICFILES.FPT. If you are using PKWare's PKZIP utility, you can compress these files into a self-extracting executable file named PICDBF.EXE by typing the following commands at the MS-DOS command prompt:

   PKZIP picdbf picfiles.dbf
   PKZIP picdbf picfiles.fpt
   ZIP2EXE picdbf

Add the following code to the first program in your project:

   * This code assumes the data file to be extracted is named
   * PICFILES.DBF. The example tested for this article was over 5 MB,
   * and compressed to 1.3 MB. The K value of 240 used in the RUN
   * command is an empirical value that has proven successful in our
   * tests, but your results may vary. A lower value may be possible.

   IF !FILE('picfiles.dbf') OR !FILE('picfiles.fpt')

      * The data is shipped as a self-extracting executable with the
      * name PICDBF.EXE. It may be wise to include the -o parameter to
      * overwrite files when extracting databases.

      RUN /240 picdbf.exe -o

      * The WAIT window below will keep FoxPro from continuing in
      * multithreaded operating systems such as Microsoft Windows NT.

      DO WHILE !FILE('picfiles.fpt')
         WAIT WINDOW 'Extracting files...' TIMEOUT 5
      ENDDO

   ENDIF

The file-compression utilities mentioned above are manufactured by vendors independent of Microsoft; we make no warranty, implied or otherwise, regarding these products' performance or reliability.