When using gfix I have not found a way to have some system table check
for data integrity : RDB$RELATION_CONSTRAINTS & RDB$REF_CONTRAINTS
where I could find some 'orphaned' rows

I understand the following
when creating as FK from tableA to tableB
there should an entry in

RDB$RELATION_CONSTRAINTS describing the name of the constraint, the
relation it applies to (TABLEA) and the name of the index to be used
(in the example of an FK)

RDB$REF_CONTRAINTS describing what PK is to be used and what action to
be taken (eg RESTRICT) when deleting or updating. (then it's simply a
matter of rereading RDB$RELATION_CONSTRAINTS to find out which table
it applies to.

I have found cases where there was 1 record in
RDB$RELATION_CONSTRAINTS and none on RDB$REF_CONTRAINTS and 1 example
of the contrary. FB does not choke on this and obviously this should
not happen in a live dn scenario, but can apparently happen with
developement databases.

QUESTIONS:

1:does gfix perform a sanity check on those tables and how to have it
do so ?

2:any idea on how this can happen & what are the steps to clean it
(there could be info I am missing).

3: Also to delete an index is it enough to delete the corresponding
entry in RDB$INDEX_SEGMENT or is there more to it ?

Thanks in advance
Didier