ORA-00845: MEMORY_TARGET not supported on this system

 11g 中有一個新特新 MEMORY_TARGET，修改時遇到了 ORA-00845

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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

      來自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.

      簡單來說就是 MEMORY_MAX_TARGET 的設置不能超過 /dev/shm 的大小：

1 2	[oracle@FWDB FWDB]$ df -h | grep shm tmpfs                 2.0G     0  2.0G   0% /dev/shm

    可以通過修改/etc/fstab文件來增大/dev/shm的大小：

1 2	[root@FWDB ~]# cat /etc/fstab | grep tmpfs tmpfs                   /dev/shm                tmpfs   defaults,size=4G 0 0

      現在可以通過重啓使這個配置生效，也可以通過重新掛載來修改其大小：

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[root@FWDB ~]# mount -o remount,size=4G /dev/shm [root@FWDB ~]# df -h | grep shm tmpfs                 4.0G     0  4.0G   0% /dev/shm

      再次啓動數據庫，沒有報錯了。