Oracle11g - ORA-00845: MEMORY_TARGET not supported on this system

操作系统	CentOS release 6.5 64-bit
数据库版本	Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production

启动数据库的时候，遇到ORA-00845: MEMORY_TARGET not supported on this system这个错误。根据Oracle官网解释

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. 

有两种解决方案：

1. Reduce the value for the memory_target parameter

2. Increase the temporary memory allocation on the server. 

我先检查了我本地/dev/shm的大小：

df -h /dev/shm

然后发现才2G，于是我试图调大到4G，执行如下命令

mount -t tmpfs shmfs -o size=4g /dev/shm

然后为了确保系统重启后也能生效，我又修改了/etc/fstab这个文件，改成如下

然后Oracle DB启动成功，也能正常访问。但是我启动Jboss连接该数据库，得到了如下错误

ORA-27102: out of memory

Linux-x86_64 Error: 12: Cannot allocate memory

然后在网上搜了一堆解决方案，都没有解决该错误，然后试图调小memory_target和MEMORY_MAX_TARGET参数值的大小，

alter system set memory_max_target=1024m scope=spfile;
alter system set memory_target=1024m scope=spfile;

--查看sga和memory参数，看修改是否正确
show parameter sga;
show parameter memory;

然后重启数据库，再重启jboss，成功解决该问题。

shutdown immediate;
startup;