ORA-00845: MEMORY_TARGET not supported on this system

今天晚上新装一台Oracle 11g的数据库，打算将SGA设大一点，知道 11g 中有一个新特新 MEMORY_TARGET，于是尝一下鲜，谁知报了个 ORA-00845，报错比较容易迷惑人，不借助Google真得想半天：

SQL> alter system set memory_max_target=3G scope=spfile ;

System altered.

SQL> alter system set memory_target=2G scope=spfile ;     

System altered.

SQL>
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup ;
ORA-00845: MEMORY_TARGET not supported on this system
      来自Oracle的官方解析是：

Starting with Oracle Database 11g, the Automatic Memory Management feature requires more shared memory (/dev/shm)and file descriptors. The size of the shared memory should be at least the greater of MEMORY_MAX_TARGET and MEMORY_TARGET for each Oracle instance on the computer. If MEMORY_MAX_TARGET or MEMORY_TARGET is set to a non zero value, and an incorrect size is assigned to the shared memory, it will result in an ORA-00845 error at startup.

      简单来说就是 MEMORY_MAX_TARGET 的设置不能超过 /dev/shm 的大小：


[oracle@FWDB FWDB]$ df -h | grep shm
tmpfs                 2.0G     0  2.0G   0% /dev/shm
      还真是撞到这个枪口上了：

      马上把它加大：


[root@FWDB ~]# cat /etc/fstab | grep tmpfs
tmpfs                   /dev/shm                tmpfs   defaults,size=4G 0 0
      现在可以通过重启使这个配置生效，也可以通过重新挂载来修改其大小：

[root@FWDB ~]# mount -o remount,size=4G /dev/shm
[root@FWDB ~]# df -h | grep shm
tmpfs                 4.0G     0  4.0G   0% /dev/shm
      再次启动数据库，没有报错了。

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[root@aaaprod-db ~]# vi /etc/fstab

/dev/rootvg/LogVol02  /                      ext3  defaults      1 1

/dev/rootvg/LogVol01  /tmp                  ext3  defaults      1 2

/dev/rootvg/lvol0    /ebao                  ext3  defaults      1 2

/dev/rootvg/lvol1    /backup                ext3  defaults      1 2

LABEL=/boot            /boot                  ext3  defaults      1 2

tmpfs                  /dev/shm              tmpfs  defaults,size=16g      0 0

devpts                /dev/pts              devpts gid=5,mode=620 0 0

sysfs                  /sys                  sysfs  defaults      0 0

proc                  /proc                  proc  defaults      0 0

/dev/rootvg/LogVol00  swap                  swap  defaults      0 0

"/etc/fstab" 10L, 769C written
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链接：http://www.cnblogs.com/killkill/archive/2010/09/10/1823690.html