This is a follow-up with more informathion to think about.

If I mark the database as read-only and run SELECT many times then in
16K transactions I got the error

"internal gds software consistency check (cannot find tip page (165),
file: tra.cpp line: 2444)"

This problem is described in one of Borland's pages
http://dn.codegear.com/article/30208

I think this is a problem and is qualified as "skeleton in closet" and
has been existing for a long time.