Subject Notice to DBak users: significant UDF restore bug
Author Geoff Worboys
Hello DBak users,

(and apologies to non-DBak users, this is the best way I know
to try and contact those who may have downloaded and be using
the product).

I have discovered a significant bug in DBak restore and rebuild
when using UDFs with BY DESCRIPTOR arguments.

If you do NOT use BY DESCRIPTOR on your UDF arguments then you
can ignore this warning.

DBak backups produced from valid databases (databases that were
not created by a DBak restore or rebuild) are valid and do not
need to be altered. DBak v1.4.2 and later will be able to
restore valid databases from these backups.

The problem:

If you restore or rebuild a database using DBak then any
BY DESCRIPTOR arguments will be transparently translated to

In my own examples of such UDFs, all use of the UDF (in stored
procedures, triggers and select statements) will create and
execute without error, but the results may be unexpected and
unpredictable. The fact that you may not receive an error
makes the implications of this bug potentially quite serious
(hence this notice).

Databases now in use after being restored or rebuilt by DBak
are susceptible to problems - and backups (gbak or dbak) taken
from these suspect databases will also carry the problem.

If you use DBak and your databases have UDFs with BY DESCRIPTOR
arguments then it is important that you download the latest
update to DBak (v1.4.2).

Note that this WILL effect people that use DBak and also use
the fbudf UDF library. Users of only the ib_udf library are
not effected. Obviously if you have your own UDFs you will
(hopefully) know whether you BY DESCRIPTOR or not.

More information about the problem and how to repair effected
databases that were created with DBak restore/rebuild is
provided in the packages (in a file called readme_udfbug.txt).

Geoff Worboys
Telesis Computing