Hi Chris, Christian Antognini schrieb: > Which is the definition of the table KLM_TEST? I ask because I noticed > that the query contains some hidden columns and also a call to > SYS_OP_NOEXPAND (see below). It might be that you are processing some > data not supported by PX. This hint was great: There has been a user defined object type in the table definition. This prevented the table from parallelizing, as well as it slowed down any simple select on it. You know, what I posted here have been tests to simplify the case described in the very beginning of this thread, you remember the huge merge? So, furthermore, the target table of my merge has had a trigger specified on written columns, what prevents DML parallelization as well. The link for infos about parallel DML is: http://download.oracle.com/docs/cd/B19306_01/server.102/b14223/usingpe.htm#CACEJACE Chris, Ian, William and all other contributors to this thread: Thanks a lot - it's a great thing that you are spending your valuable time for shooting other people's trouble! Best regards Martin Klier -- Usn's IT Blog for Linux, Oracle, Asterisk http://www.usn-it.de -- //www.freelists.org/webpage/oracle-l