I'd be interested in the definitive answer as well. Based on what it does (described in reasonable detail at http://docs.oracle.com/cd/E11882_01/server.112/e16638/instance_tune.htm#PFGRF94543) I suspect there will be some, but not significant, impact. After all, "By default, SQL monitoring automatically starts when a SQL statement runs parallel, or when it has consumed at least 5 seconds of CPU or I/O time in a single execution." and so all you are doing is adding those statements that don't run in parallel, and don't consume 5 seconds I/O or CPU. Depending on the load type of your environment, that might not affect many/any statements. But it is (yet another) area I have not studied in detail. /Hans On 15/03/2013 12:44 PM, Josh Collier wrote: > Does the /*+ monitor */ hint affect performance at all? > Thanks for your help! -- //www.freelists.org/webpage/oracle-l