David, In my mind ISM is related to shared memory, could it be used for private memory allocation ? thanks --romas On Tue, Oct 7, 2008 at 6:38 PM, David Miller <David.J.Miller@xxxxxxx> wrote: > Hi Roman, > > I believe this was obsoleted in Oracle 10.2, which is why you don't see it > do > anything. > > The idea behind the parameter (_use_ism_for_pga) was that Solaris only > allowed large pages for ISM segments prior to Solaris 9 and in Solaris 9, > using large pages for non-ISM segments required manual intervention. > > In Solaris 10, large pages became usable for many different kinds of memory > depending on the allocations for each. Thus it became possible to use > large pages for the PGA without having to put it in ISM. > > But it still will depend on how the PGA is allocated. With 10.2.0.3, you > can specify the "_realfree_heap_pagesize_hint = 4194304" and it will > use 4 MB pages for the heap. These won't be ISM, but using "pmap -xs" > will show the segments with a pagesize of 4M (assuming you're on SPARC). > > The benefits of this will depend entirely on how your application uses > the PGA. With large hash or sort areas needed, large pages can help > performance significantly. For other applications, the benefit may > be minimal. > > Regards, > > Dave Miller >