--- In firebird-support@yahoogroups.com, "Fikret Hasovic"
<fhasovic@y...> wrote:

> TestCase: Create simple database and one table with one field of

type

> TIMESTAMP default 'Now'. Fill it with some data, then change type
> from TIMESTAMP to DATE and try to make backup.
> It fails with error: "Arithmetic overflow or division by zero has
> occured. arithmetic exception, numeric overflow or string

truncation."

It's not a bug, as designed. When you change type of column FB
changes description in system tables and since this moment
a) stores new modifications in new format
b) reads old data in old format and converts to new one on
representation.

Perhaps fact than gbak don't do the same can be estimated as it's
bug.

> Any help? Or I should make new Db and pump data from old to new?

After you change type of the column make

Update This_Table Set Changed_Column=Changed_Column

FB will read old data, convert to new format and store in new format.

Best regards,
Alexander.