SQL & PL/SQL

Hello all,

I have 2 DB's and I would like to merge records from A into B with dml error logging through a db link.
Exemple:
merge into B@dblink
using (select ... from A where...)
when matched then
...
when not matched then
...
log errors into err$_A reject limit unlimited;

When I use this, and exception is thrown:

ORA-02291: integrity constraint (B.constraint_name) violated - parent key not found
ORA-02063: preceding line from dblink

I've got no idea of what causes this.
Could anyone please help me ?

Thanks !

Regards,

TDE.