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Accessing DBF Tables over 2GB in Visual FoxPro with Advantage Database Server


Visual FoxPro applications are constantly challenged by the constraint that only allows access to DBF tables under 2GB. Many VFP applications have been running for years, and during that time the amount of data has grown to test the 2GB limit. Developers are forced to find creative ways to maneuver around the 2GB limit, including archiving data and splitting one table into multiple tables.

With Advantage Database Server (ADS) you can access tables over 2GB because ADS natively supports the DBF/CDX format.

How does it work?

Advantage can preserve the DBF file format while allowing the table to grow beyond the 2GB limit of the FoxPro driver. Advantage does this by using a 64-bit unsigned integer to calculate the file offsets, while VFP uses a 32-bit signed integer. Using a larger value to track the file offsets allows Advantage to access DBF files that exceed 2GB in size. However, the native VFP driver will no longer recognize this file as a valid table.

When using Advantage the file size is limited by the operating system and available disk space. When using one of the latest file systems (i.e. NTFS, NSS) the file limit size limit is in Exabytes ( 1EB = 1 billion GB). A more realistic limitation is on the number of records that can be stored in the table. This is currently limited to 2 billion records therefore the maximum size of your table will be 2 billion times your record size.

Typical Visual FoxPro Local Data Access          Accessing a Table >2GB with Advantage




What data access options are available?

Advantage has a variety of data access methods for many different environments.  FoxPro developers should use the Advantage ODBC driver or OLE DB Provider.  Other available clients include .NET, CA-Clipper, CA Visual Objects, Delphi, PHP, Java, and Perl.

How much does it cost?

The above solution is free.  The ODBC and OLE DB drivers can be downloaded free at  Advantage also includes a free Local Server (ALS) that can be embedded royalty free with your application and has many of the features contained in the full Advantage Database Server client/server product.  Once you have seen the power, reliability, stability, features, and ease of implementation of Advantage, you will want to fully integrate it into your VFP application.  With the full client/server product, Advantage Database Server, you will instantly receive benefits such as encryption, hiding your data from users, replication, hot backup, concurrent data access with other technologies to continue growing and extending your application, and others.


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