Scenario:
SQL> STARTUP
ORA-00845: MEMORY_TARGET not supported on this system
Cause:
On Linux systems, the cause of this error is an insufficient /dev/shm allocation. The total memory size of the SGA and PGA, which sets the initialization parameter MEMORY_TARGET or MEMORY_MAX_TARGET, cannot be greater than the shared memory file system (/dev/shm) on your operating system.
Background:
Automatic Memory Management (AMM) has been updated in Oracle ASM 11g Release 2. It manages both the SGA and PGA together. It is managed by the Memory Manager Process (MMAN). In this release, note the following changes to AMM:
•It uses MEMORY_TARGET instead of SGA_TARGET
•It uses MEMORY_MAX_TARGET instead of SGA_MAX_SIZE (defaults to MEMORY_TARGET)
•It uses memory allocated by /dev/shm
If the value of max_target is set to a value greater than the allocation for the /dev/shm size, then you may encounter the error ORA-00845: MEMORY_TARGET not supported on this system.
Solution:
Check the size of your MEMORY_TARGET:
SQL> show parameter MEMORY_TARGET
Verify that /dev/shm is properly mounted.
[TEST1011@ /home/oracle] df -h
shmfs 1.0G 0 1.0G 0% /dev/shm <<< Verify that this has enough space. In this case, is has less than the size allocated for MEMORY_TARGET.[TEST1011@ /home/oracle] df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
16G 8.7G 5.9G 60% /
/dev/hda1 99M 12M 83M 13% /boot
shmfs 1.0G 0 1.0G 0% /dev/shm
Resize /dev/shm properly. Ask assistance from your Unix Admin.
[root@oel53 ~]# umount /dev/shm
[root@oel53 ~]# mount -t tmpfs shmfs -o size=3g /dev/shm
[root@oel53 ~]# df -h
To make this change persistent across system restarts, add an entry in /etc/fstab similar to the following:[root@oel53 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
16G 8.7G 5.9G 60% /
/dev/hda1 99M 12M 83M 13% /boot
shmfs 3.0G 0 3.0G 0% /dev/shm
shmfs /dev/shm tmpfs size=3g 0
[root@oel53 ~]# cat /etc/fstab/dev/VolGroup00/LogVol00 / ext3 defaults 1 1
LABEL=/boot /boot ext3 defaults 1 2
tmpfs /dev/shm tmpfs defaults 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
shmfs /dev/shm tmpfs size=3g 0