The BACKUP DATABASE statement produces a compressed file, you set the compression level between 0 and  with 6 as default.

I  need to be able to generate binary diffs between BACKUPs, which would ideally be fairly small and represent the difference between the backup on day 1 and 2.

With standard compression (= 6 in EDB SQL), the binary forms of backup files for the same database on 2 days are very different, i.e. the "ZIPPIING" process is jumbling up the files, so the diff file is almost as big as the backup file itself.

With the compression set at "0" I get large backup files, and the diff file is much smaller. However I don't know whether "0" compression represents "no compression at all" or just the lowest level Tim has chosen to apply.

Is anyone else working with BACKUP enough to give me some more detailed idea of what actually happens when the command is called. I know that the ZLib compression libraries are used, and that Tim has written some "custom code" to manage the various levels of compression, but not a lot more!

Adam,

Yes, 0 level compression means no compression.

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Fernando Dias
[Team Elevate]