We are in a testing phase of migrating a client from an As400 database and application to our Firebird (2.5) based delphi application.  

Every night we do the following :

delete most of the data in the firebird database

backup and restore the database using gbak

re-import data from the AS400 database.

I have experienced two cases where data definitions appear to have changed after the backup/restore sequence.

1) A Field defined as varchar(1000) in my original database were changed to blob sub type 1 after a backup and restore.

2) A regular table in the original database showed up as a Global Temporary Table after a backup and restore.

The two issues happened during separate backup/restore sequences and have only occurred once, and have not repeated.  It was easy enough to correct, but concerns me that other entities may have changed that I am not noticing yet.

Perhaps I am doing something incorrectly in the GBAK parameters?

Anyone experience this?