最近由于修改了数据库的MEMORY_TARGET却忘了修改MEMORY_MAX_TARGET，数据库重启时，连不上数据库，数据库实例启动不了，
从sqlplus进入（注意：如果服务器端同时也安装了客户端，应该从服务器端的SqlPlus进入，否则 / as sysdba会不成功）：
Enter user-name: / as sysdba;
Connected to:
Oracle Database 11g Enterprise Edition......
SQL>startup;
ORA-00837: Specified value of MEMORY_TARGET greater than MEMORY_MAX_TARGET
Connected to:
Oracle Database 11g Enterprise Edition......
SQL>startup;
ORA-00837: Specified value of MEMORY_TARGET greater than MEMORY_MAX_TARGET
于是手动修改数据库参数文件：app/Administrator/product/11.1.0/db_1/database/SPFILEORCL.ORA
打开参数文件显示：
*.memory_max_target=5108662272
*.memory_target=5368709120
果然是memory_target>memory_target, 于是修改memory_target成4048551936（从app\Administrator\admin\orcl\pfile\init.ora里查到上次的值),
再启动数据库，成功！