Hi, I'm using Firebird 1.0.2 and
here are the steps i've made:

1. FORGOT to execute: update PESSOA set CONTATO = 0 where CONTATO is null;

2. update RDB$RELATION_FIELDS set RDB$NULL_FLAG = 1 where (RDB$FIELD_NAME =
'CONTATO') and (RDB$RELATION_NAME = 'PESSOA');

3. backup

4. impossible to restore due arithmetic truncation or string overflow while
recovering data from table PESSOA because some records have the field
CONTATO null

I already tried to update the RDB$NULL_FLAG to null, then backup and
restore. But doesn't work.

Any way i can back the GDB to a normal state?

ps.: Lession learned: 'Pay attention when messing with system tables and
don't mess with system tables unless extremely necessary.'