I remember a nice blog post by Jonathan Lewis ( http://jonathanlewis.wordpress.com) for safe/unsafe usage of hints. I just don't have the direct link to it. Thanks, Galo On Mon, Aug 15, 2011 at 10:51 AM, Ric Van Dyke <ric.van.dyke@xxxxxxxxxx>wrote: > Keep in mind that hints aren’t hints, they are directives. Hints will be > followed unless the optimizer can’t use the hint (tell it to use an index > that doesn’t exist for example). **** > > ** ** > > There are good hints and there are bad hints.**** > > ** ** > > Good hints help the optimizer do something, bad hints force the optimizer > to do something.**** > > ** ** > > Examples: The cardinality hint is considered good because it can let the > optimizer know how many rows will come back from a table when it can’t know > (for example a Table that has been casted from a string). It can also “go > bad” if the number of rows changes over time (the number of rows cannot be > set dynamically as far as I know, other than dynamic SQL which has its own > issues). **** > > ** ** > > A join hint (use_nl for example) is considered bad because it forces the > optimizer to pick that join every time. This might be true for the moment > but is it always going to be true? Same for index or full table scan hints. > **** > > ** ** > > Hints are great for testing and should only be in production code as a > “last resort”. **** > > ** ** > > +--+--+--+--+--+--+--+--+--+--+--+--+--+--+**** > > Ric Van Dyke**** > > Education Director**** > > Hotsos Ltd.**** > > ** ** > > Hotsos Symposium March 4-8 2012**** > > Make your plans to be there now!**** > > [image: Description: 2012_sym_logo_invert]**** > > ** ** > > *From:* oracle-l-bounce@xxxxxxxxxxxxx [mailto: > oracle-l-bounce@xxxxxxxxxxxxx] *On Behalf Of *Orlando L > *Sent:* Monday, August 15, 2011 01:44 > *To:* oracle-l@xxxxxxxxxxxxx > *Subject:* Hints**** > > ** ** > > Hello all, > > Are hints in queries considered bad, if so why. > > Orlando. > > **** > -- Regards GBA