ORA-00845: MEMORY_TARGET not supported on this system

今天数据库登录时候报错   ORA-00845: MEMORY_TARGET not supported on this system

查阅资料：

ORA-00845: MEMORY_TARGET not supported on this system

Cause: The MEMORY_TARGET parameter was not supported on this operating system or /dev/shm was not sized correctly on Linux.

Action: Refer to documentation for a list of supported operating systems. Or, size /dev/shm to be at least the SGA_MAX_SIZE on each Oracle instance running on the system.

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 orMEMORY_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 

 意思大概就是说：当MEMORY_TARGET或者SGA_MAX_SIZE 参数设置的数值/dev/shm时就会报这个错误。或者 /dev/shm没有挂载的时候也会报这个错误   修复完成之后.做了一个小实验 以记录并验证。

    第一个为/dev/shm  未挂载的情况下会报这个错误。

此时数据库是打开的

SQL> select status from v$instance;

STATUS
------------
OPEN

查看 /dev/shm  状态

[root@lh ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda3              28G   23G  3.6G  87% /
/dev/sda1              99M   12M   83M  13% /boot
tmpfs                1006M     0 1006M   0% /dev/shm
是挂载的 
现在卸载 /DEV/SHM

[root@lh ~]# umount /dev/shm
umount: /dev/shm: device is busy
umount: /dev/shm: device is busy
遇到这种情况用fuser 解决

[root@lh ~]# fuser -km /dev/shm
/dev/shm:             9297m  9299m  9301m  9305m  9307m  9309m  9311m  9313m  9315m  9317m  9319m  9321m  9323m  9325m  9327m  9329m  9331m  9372m  9384m  9389m  9397m  9404m  9416m  9428m  9431m  9433m
[root@lh ~]# umount /dev/shm
[root@lh ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda3              28G   23G  3.6G  87% /
/dev/sda1              99M   12M   83M  13% /boot
现在/dev/shm已经卸载  切回sqlplus

SQL> select sysdate from dual;
ERROR:
ORA-03114: not connected to ORACLE
已经不再连接ORACLE，返回重新连接
SQL> startup
ORA-00845: MEMORY_TARGET not supported on this system

报错

重新挂载 /dev/shm 再连接

[root@lh ~]# mount /dev/shm
[root@lh ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda3              28G   23G  3.6G  87% /
/dev/sda1              99M   12M   83M  13% /boot
tmpfs                1006M     0 1006M   0% /dev/shm
SQL> startup
ORA-00845: MEMORY_TARGET not supported on this system
SQL> startup
ORACLE instance started.

Total System Global Area  839282688 bytes
Fixed Size                  2233000 bytes
Variable Size             553651544 bytes
Database Buffers          281018368 bytes
Redo Buffers                2379776 bytes
Database mounted.
Database opened.
SQL> 

数据库成功打开。

另一种情况，

MEMORY_TARGET或者SGA_MAX_SIZE设置大于/dev/shm

SQL> show parameter memory


NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
hi_shared_memory_address             integer     0
memory_max_target                    big integer 804M
memory_target                        big integer 804M
shared_memory_address                integer     0
SQL> alter system set memory_target=1200M scope=spfile;

System altered.

SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORA-00845: MEMORY_TARGET not supported on this system

报错！！

这时候增大  /dev/shm  即可

[root@lh ~]# mount -o remount,size=2048M /dev/shm
[root@lh ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda3              28G   23G  3.6G  87% /
/dev/sda1              99M   12M   83M  13% /boot
tmpfs                 2.0G     0  2.0G   0% /dev/shm
再打开ORACLE

SQL> startup
ORACLE instance started.


Total System Global Area 1252663296 bytes
Fixed Size                  2227944 bytes
Variable Size             805306648 bytes
Database Buffers          436207616 bytes
Redo Buffers                8921088 bytes
Database mounted.
Database opened.
SQL>