Double Underscore Sign In Parameters....

Hi there,
DB: 11106
OS: Win Xp Proff
I understand that with the underscore prefixed , the parameters are called undocumented parameters. But I am seeing at times, parameters having 2 undrescores attached to it too. What's these parameters and why we have two underscores attached to them? For example,
SQL> select ksppinm,ksppstvl,ksppstdvl   2 from x$ksppcv a,x$ksppi b
  3 where a.indx=b.indx and b.ksppinm like '%shared_io%';

KSPPINM                        KSPPSTVL

------------------------------ ------------------------------
----------------


__shared_io_pool_size          4194304                        4M

_shared_io_pool_size           4194304                        4M

_shared_iop_max_size           536870912                      512M

_shared_io_pool_buf_size       1048576                        1M

_shared_io_pool_debug_trc      0                              0

_shared_io_set_value           FALSE                          FALSE

6 rows selected.
You can see that the first one is having a double underscore attached. Similarly, in PGA also , there is __pga_aggregate_target parameter. If anyone can explain this, it would be really great. Thanks
Aman.... Received on Thu Oct 09 2008 - 21:57:08 CDT