Reset Oracle Parameter Value

select name,value,isdefault,isses_modifiable,issys_modifiable,
isinstance_modifiable,isdeprecated,
from v$parameter;

alter system reset some_param scope=both sid='*' ;


alter system reset some_param scope=spfile sid='*' ;

alter system reset some_param scope=memory sid='*' ;


scope =BOTH/SPFILE/MEMORY



For string parameters, setting to an empty string will restore the default.

ALTER SYSTEM SET parameter = '' scope=SPfile;


For any parameter the RESET option will restore the default.
ALTER SYSTEM RESET parameter scope=SPfile sid='*' ;

note
When resetting a parameter, you must specify sid=mySid or sid='*' even for non-RAC instances.


ALTER SYSTEM RESET memory_target scope=SPfile sid='*' ;


donot do that with memory parameter, other oracle will not startup then restart oracle services

memory_target will bet set to zero.

then reset memory_target again