I just came across this question on Stackoverflow:
http://stackoverflow.com/questions/38070209/what-is-this-file-fdr-in-the-directory-firebird

The question is: "what is this file .fdr in the directory Firebird . For
me, it weighs 16 gb. Is this a transaction log ? Or how to reduce it ?"

I've never heard of such a file, does anyone have an idea what it could be?

Mark
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Mark Rotteveel