Subject Re: [firebird-support] use of -USE_ALL_SPACE
Author Ann Harrison

The default (ie, if you leave this parameter off the command line) is to
> leave 20% of each page for future updates.

Unless the code has changed (for the worse) relatively recently, the amount
of space left depends on the size of the uncompressed record data. When
storing new records, Firebird normally leaves room for a fragmented record
header (16 bytes, from memory) for each record on the page. So with a very
tiny record, the page would be about half full (16 bytes free for each
plus its normal header). With very large records, the page might be over
full (leaving only 16 bytes of space).

> After the restore is completed, and as far as I am aware, the normal
> 80-20% usage continues on new pages.
> Subject to the same caveat, once a database has been created with
USE_ALL_SPACE, new records will be stored on pages without leaving
extra room.

Remember, gbak is nothing but an application that happens to know a
lot about metadata and interdependencies. It has no special access to
the database.

Good luck,


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