Unsuccessful metadata update, TABLE xyz, too many versions

Each change you make in table's structure is recorded in RDB$FORMATS system table. When you make 255 changes, you must do a backup and subsequent restore - which resets counter for all tables.

Why is this recording of changes needed? Well, imagine you have a table column, type INTEGER, and you change it to DECIMAL(16,2). When this happens, you may have thousands or millions of records in that table. Internal representation (binary) of these two types is not the same - so it would mean that Firebird needs to rewrite all those records. Instead of doing that, Firebird remembers that those old records have INTEGER format and converts them on-the-fly when reading. New records get stored in DECIMAL(16,2) format.

Do you find this FAQ incorrect or incomplete? Please e-mail us what needs to be changed. To ensure quality, each change is checked by our editors (and often tested on live Firebird databases), before it enters the main FAQ database. If you desire so, the changes will be credited to your name. To learn more, visit our add content page.

If you are a commercial tool maker and your tool features a great way to handle the issue written about in this FAQ, please check out our advertisement page.