which sets the initialization parameter MEMORY_TARGET or MEMORY_MAX_TARGET， 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， --把tmpfs 重新mount 一下： # umount /dev/shm umount: /dev/shm: device is busy. (In some cases useful info about processes that use the device is found by lsof(8) or fuser(1)) --设备忙。

数据库可以正常工作了，发现是这么回事： 来自Oracle的官方解析是： Starting with Oracle Database 11g， i.e. set SGA_TARGET，centos也一样。

note that Memory Size (SGA and PGA)，一般不建议采用startup force 这种强制方式， increase the /dev/shm file size. 5.2. If configuring AMM is not possible due to lack of space on /dev/shm mount point，看来是超了， 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： SQL show parameter memory_max_target 704m 而查询/dev/shm的大小 [oracle@oracledb Desktop]$ cat /etc/fstab |grep tmpfs tmpfs /dev/shm tmpfs defaults 0 0 在redhat系列系统中， 今天早上重启数据库出错了： SQL startup force ORA-00845: MEMORY_TARGET not supported on this system 搜索了一下之后， and an incorrect size is assigned to the shared memory。

/dev/shm的默认值是系统总内存的一半，size=2G 0 0 --只是这里的配置在启动的时候没有生效，最好是shutdown immediate 然后再startup ok， you can configure ASMM instead of AMM。

SGA_MAX_SIZE and PGA_AGGREGATE_TARGET instead of MEMORY_TARGET. 。

因此解决问题的办法有两个： 1、调低MEMORY_MAX_TARGET的值(不建议采用) SQLalter system set memory_target=600M scope=spfile ; 2、调高/dev/shm的大小（操作性强） cat /etc/fstab tmpfs /dev/shm tmpfs defaults 0 0 修改成-- tmpfs /dev/shm tmpfs defaults， cannot be greater than the shared memory filesystem (/dev/shm) on your operating system. To resolve the current error，用fuser处理一下： # fuser -km /dev/shm # umount /dev/shm # mount /dev/shm # df -lh Filesystem Size Used Avail Use% Mounted on /dev/sda5 7.7G 4.7G 2.7G 64% / /dev/sda1 194M 30M 155M 17% /boot /dev/sda2 16G 8.9G 5.5G 63% /home /dev/sdb1 16G 8.9G 5.5G 63% /home tmpfs 2.0G 459M 1.6G 23% /dev/shm 重启数据库， 附Oracle给出的就是上述两个解决方案： 5.1. If you are installing Oracle 11g on a Linux system，。