March 20, 1997 6:30 PM ET
FoxPro bug rare but deadly for data
By Juan Carlos Perez

  A rare bug that can corrupt data in Visual FoxPro 5.0 has been found.

Microsoft Corp. acknowledged the bug and is trying to fix it. The bug's occurrence seems fairly rare and has been reported by only one user so far, officials said.

"This is definitely a known bug, but it's complicated to reproduce. It's a rare situation, but data corruption is a serious problem and we want to address that," said David Lazar, Visual FoxPro product manager.

Microsoft plans to have the bug fixed in the next Visual FoxPro release, whose shipping date hasn't been set. In the meantime, a paper detailing the bug and suggesting some workarounds is in final edits now and will be posted on the Microsoft Web site soon, Lazar said.

The user who reported the bug said the problem seems to be tied to low-memory conditions.

"When you open a remote view, FoxPro creates a local image of the back-end table. Depending on how much you've got in the data buffer, the last records in the file can get corrupted when you swap memory and open another remote view," said the user, who requested anonymity.

The user, who first contacted Microsoft in early January, noticed the problem when he was testing an application and realized records were being lost.

"If I hadn't been testing the application, I wouldn't have noticed," said the user, who uses Visual FoxPro as front end to a Microsoft SQL Server database.

Microsoft support suggested a few workarounds, such as breaking down the data into smaller sets of records and writing a two-line test program. But those solutions aren't feasible for this user, because they are too time-consuming.

The problem seems to arise when he uses FoxPro to synchronize the two back-end databases because the process involves large tables and eats up a lot of memory, he said. So he now runs that operation only when he has to, about twice a month. He checks for data corruption errors manually.

"My confidence in the data integrity is gone," he said.

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