hi if you have histograms for those columns in your predicates then for each cursor you would have X cursor per different column value, this is with SIMILAR with FORCE you still have 40-60 child cursors? thanks -- LSC On 9/27/07, Terry Sutton <terrysutton@xxxxxxx> wrote: > > I'm trying to resolve a client situation which involves a lot of hard > parsing and library cache latch waits, and I'm hoping to bounce some ideas > off people. > > The database is 10.2.0.3 on Solaris. cursor_sharing was set to > 'SIMILAR'. No, they don't use bind variables, and that's not going to > change soon. > > I've found that we have a lot (40-60) of child cursors for some SQL > statements. When I look at v$sql_shared_cursor I find that most of the > child cursors have Y for bind_mismatch. But when I look at > v$sql_bind_metadata the DATATYPE and MAX_LENGTH are identical for all the > cursors. So I'm concluding that the bind mismatches are due to the > cursor_sharing='SIMILAR' parameter causing new child cursors due to > different values for the literals which are being converted to bind > variables (please correct me if my conclusion is unwarranted). > > So I'm trying to figure how to solve this issue (short of having the > client use bind variables properly). It seems that cursor_sharing='FORCE' > would eliminate the bind mismatch problem, since the values of the literals > would all convert to the same bind variables. We've changed the > cursor_sharing setting, but we're still having library cache latch waits. > I'm wondering if the problem is that we still have the child cursors in the > shared pool, and each soft parse has to go through the list of child cursors > for a given parent to find a matching one. Would flushing the shared pool > solve this part of the problem? Or am I missing something else obvious? > I'm a bit wary of flushing the shared pool on a DB that is already having > contention problems, unless I'm very confident of having it resolve the > issue. > > Any input is welcome, even if it's "hey idiot, you missed this". :-) > > --Terry >