想改shared_pool_size的值，可是不成功，不知道要该系统的什么值，各位大虾知道吗？
SQL> alter system set shared_pool_size=50m scope=both;
alter system set shared_pool_size=50m scope=both
*
ERROR at line 1:
ORA-02097: parameter cannot be modified because specified value is invalid
ORA-04033: Insufficient memory to grow pool
环境：RedHat AS 3，oracle 10g
/etc/sysctl.conf相关内容：
kernel.core_uses_pid = 1
kernel.shmmax = 2147483648
kernel.shmmni = 4096
kernel.shmall = 2097152
kernel.sem = 250 32000 100 128
fs.file-max = 65536