Thanks for quick answer. I'll try to describe my situation more
precisely. I connect to embedded firebird instance through Jaybird
JDBC driver. There are few actions performed:
1. Create tables (about 300 of them).
2. Alter those tables by adding basic constraints (pk, fk, unique).
3. commit
4. Fill them with a lot of data.
5. commit

On last commit i get FBSQLException:
violation of FOREIGN KEY constraint "INTEG_904" on table "some_name"

If this db supports only immediate constraints, why do i get this
exception at commit time, and not when inserting data? It seems very
weird... That is why i assumed that this db supports only deferred
constraints (another reason: i had problems finding info about it in
docs). What could be the reason? Thanks in advance.