使用虚拟机时，机器实在太卡，原来虚拟机会把你所分配给它的内存扣死，昨天把虚拟机的内存从1.5G缩小到1G。机器果然顺畅了，不过担心的问题也出现了－－oracle的实例启动不了。
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
我不知道怎样调整MEMORY_MAX_TARGET，所以就调整/dev/shm的大小
查看原本大小
[root@Shine2 oracle]# df -h|grep shm
tmpfs 505M 75K 505M 1% /dev/shm
在文件搜索里找到6个initXXX.ora文件，随便打开两个发现memorytarget的值不同。。。
其中有一个是1G，那就1G吧。。。也不知道是什么
[oracle@Shine2 ~]$ gedit /etc/fstab
把文件中
tmpfs /dev/shm tmpfs defaults 0 0
改为
tmpfs /dev/shm tmpfs defaults,size=1G 0 0
[root@Shine2 oracle]# umount /dev/shm
出现错误：/dev/shm is busying，并提示我使用lsof命令。
lsof（list open files）是一个列出当前系统打开文件的工具。
[root@Shine2 oracle]# lsof |grep shm
lsof: WARNING: can't stat() fuse.gvfs-fuse-daemon file system /home/oracle/.gvfs
Output information may be incomplete.
pulseaudi 2997 oracle mem REG 0,16 67108904 9562 /dev/shm
[root@Shine2 oracle]# kill 2997
[root@Shine2 oracle]# lsof |grep shm
lsof: WARNING: can't stat() fuse.gvfs-fuse-daemon file system /home/oracle/.gvfs
Output information may be incomplete.
把使用该文件的进程干掉了
[root@Shine2 oracle]# umount /dev/shm
[root@Shine2 oracle]# mount /dev/shm
[root@Shine2 oracle]# df -h|grep shm
tmpfs 1.0G 400M 625M 40% /dev/shm
卸载再重新挂载后，实例终于可以启动了～哈哈
[oracle@Shine2 ~]$ sqlplus
SQL*Plus: Release 11.2.0.1.0 Production on Sat Jul 30 09:34:01 2011
Copyright (c) 1982, 2009, Oracle. All rights reserved.
Enter user-name: / as sysdba
Connected to an idle instance.
SQL> startup
ORACLE instance started.
Total System Global Area 640286720 bytes
Fixed Size 1338420 bytes
Variable Size 461374412 bytes
Database Buffers 171966464 bytes
Redo Buffers 5607424 bytes
Database mounted.
Database opened.