> Is it safe to let them open undefinitively a read only read commited
> transaction ?

Yes, because a read-only read committed transaction doesn't block
garbage collection and allows to move OIT/OAT forward.

> can it's disturb something in the server (sweep? backup ? etc..)

No.


--
With regards,
Thomas Steinmaurer (^TS^)
Firebird Technology Evangelist

http://www.upscene.com/
http://www.firebirdsql.org/en/firebird-foundation/