how to unset _smu_debug_mode in 11g database

Hi all,

Question: in 11.2.0.4 database, originally show parameter debug does not reveal this hidden parameter, after I set it to 4, I reset it, it still shows 4, then I explicitly set it to 0, show parameter debug set it to 0. But how do remove this hidden parameter, since it was NOT there originally ?

Please shed some light.

Here's the command and output:

show parameter debug «—— NO "_smu_debug_mode" appear

alter system set "_smu_debug_mode" = 4; «—- change to 4

show parameter debug

_smu_debug_mode integer 4 «—- show 4 correct

alter system reset "_smu_debug_mode" ←— reset now

System RESET altered.

show parameter debug « —- after reset , it still gives a 4