SQL> SELECT component, current_size/1024/1024 size_mb
2 FROM v$sga_dynamic_components where component='shared pool';
COMPONENT SIZE_MB
------------------------------------ ------------
shared pool 80
我们将shared_pool_size设定为70MB，小于自动调整出来的值。可以看到，shared pool没有缩小，仍然是80MB。我们再将其从80MB扩大到100MB。
SQL> alter system set shared_pool_size=100M;
SQL> SELECT component, current_size/1024/1024 size_mb
2 FROM v$sga_dynamic_components where component='shared pool';
COMPONENT SIZE_MB
------------------------------------ ------------
shared pool 100
显然，只要我们设定的值比自动调整出来的值大，就会立即生效。