If the database is running with pfile, we can change the dynamic parameters while the database is up and running but we cannot change the static parameters. If we want to change the static parameters we need to shutdown the database.
If the database is running with spfile, we can change the dynamic parameters while the database is up and running and we can also change the static parameters while the database is up and running but we need to restart the database to take effect.
SQL> alter system set someparameter=1000 scope=memmory;
"memory" scope is used only when the database is running with pfile.
If the scope is "memory" it means it is applcable for the current instance and if we restarts the database it gets the old value.
If the database is running with pfile and if we are changing the dynamic parameter, by default it takes "memory" for the scope.
"both" and "spfile" are used when the database is running with spfile.
If the scope is "both" it means it is applicable for the current instance as well as the future instances.
If the scope is "spfile' it means that it is applicable for the future instance but not the current instance. The changes will be reflected in the future instance.
If the database is running with spfile and if we are changing the dynamic parameter, by default it takes "both" for the scope.
