>We have a process that must run in the morning after some other processes. People are in the application data by the time this last process runs. One of it's tasks is to copy all files from production to another directory. This has always worked before, but recently some of the copies of the tables have become corrupt. Usually when we restart the process, they copy fine.
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>Questions on two points:
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>Why can the files be copied if they are being used in the application? There must be issues with DBF, CDX and FPT files not being in sync, but we have done this for years with no issues. How has this ever worked?
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>What are the various causes for table corruption?

I have been doing this for years - copying files while they are in use. Although I know that the results are not 100% trustworthy, I prefer to do two backups a day (noon and midnight), just in case.

As to why this is possible, I guess that for a COPY operation, exclusive access is not required. Some other operations are not possible on files in use. For example, trying to apply WinRAR to a file in use will give an error message.