Insufficient Memory Target Errors

 

4.3.2 Insufficient Memory Target Errors

On Linux systems, if the operating system /dev/shm mount size is too small for the Oracle system global area (SGA) and program global area (PGA), then you encounter the following error:

ORA-00845: MEMORY_TARGET not supported on this system. 

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.

Note:

An ORA-00845 error can also occur if /dev/shm is not properly mounted. To rule out this possibility, run the command df -k to ensure that /dev/shm is mounted. For example:

$ df -k 
 
Filesystem 1K-blocks Used Available Use% Mounted on 
shmfs 6291456 832356 5459100 14% /dev/shm

Solution
Increase the /dev/shm mountpoint size.
For example:

# mount -t tmpfs shmfs -o size=2g /dev/shm

To make this change persistent across system restarts, add an entry in /etc/fstab similar to the following:

shmfs /dev/shm tmpfs size=2g 0