问题描述：安装oracle或配置dataguard时，数据无法启动，错误信息ORA-00845: MEMORY_TARGET not supported on this system
这个错误的主要原因是tmpfs的值小于memory_target的值。
[root@dac-vm02 ~]#oerr ora 845
00845, 00000, "MEMORY_TARGET notsupported on this system"
// *Cause: The MEMORY_TARGET parameter wasnot supported on this operating system or /dev/shm was not sized correctly onLinux.
// *Action: Refer to documentation for alist of supported operating systems. Or, size /dev/shm to be at least theSGA_MAX_SIZE on each Oracle instance running on the system.
解决方案：
因此我们只需要将tmpfs的值改大一点就好了。
先来看一下memory_target的值是多大
SQL> show parameter memory_target
NAME TYPE VALUE
------------------------------------ -------------------------------- ------------------------------
memory_target big integer 1296M
SQL>
只需要将tmpfs的值设置大于800M即可，tmpfs的初始值为内存的一半
编辑/etc/tmpfs文件，将tmpfs的值定为3G
/dev/VolGroup00/LogVol00 / ext3 defaults 1 1
LABEL=/boot /boot ext3 defaults 1 2
tmpfs /dev/shm tmpfs defaults,size=3G 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/VolGroup00/LogVol01 swap swap defaults 0 0
加入红显部分即可，接着要将tmpfs重新mount一下
[root@Ginna ~]# umount tmpfs
[root@Ginna ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
28G 11G 16G 40% /
/dev/sda1 99M 22M 72M 24% /boot
[root@Ginna ~]# mount tmpfs
[root@Ginna ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
28G 11G 16G 40% /
/dev/sda1 99M 22M 72M 24% /boot
tmpfs 3.0G 0 3.0G 0% /dev/shm