ORA-00845: MEMORY_TARGET not supported on this system



# umount tmpfs
# mount -t tmpfs shmfs -o size=1200m /dev/shm

#Make the setting permanent by amending the “tmpfs” setting of the “/etc/fstab” file to look like this.

tmpfs /dev/shm tmpfs size=1200m 0 0

failed with ORA-00845

Alert Logs
Tue Jun 24 03:22:00 2014
Starting ORACLE instance (normal)
WARNING: You are trying to use the MEMORY_TARGET feature. This feature requires the /dev/shm file system to be mounted for at least 17179869184 bytes. /dev/shm is either not mounted or is mounted with available space less than this size. Please fix this so that MEMORY_TARGET can work as expected. Current available is 12824879104 and used is 8649957376 bytes. Ensure that the mount point is /dev/shm for this directory.
memory_target needs larger /dev/shm


alter system set sga_max_size=12G scope=spfile sid='*';
alter system set sga_target=12G scope=spfile sid='*';

shutdown immediate

🙂 Oracle Instance Started Successfully

Check Memory Distribution

set pagesize 10000
set linesize 1000
COLUMN component FORMAT A30

SELECT  component, current_size/1024/1024, min_size/1024/1024, max_size/1024/1024
FROM    v$memory_dynamic_components
WHERE   current_size != 0;


In this article i will discuss the Difference between these parameter and how to use them , MEMORY_TARGET & MEMORY_MAX_TARGET parameters appear in 11g .

I will depend on oracle documentation to describe these parameter :

  • SGA_MAX_SIZE sets the overall amount of memory the SGA can consume but is not dynamic.

The SGA_MAX_SIZE parameter is the max allowable size to resize the SGA Memory area parameters. If the SGA_TARGET is set to some value then the Automatic Shared Memory Management (ASMM) is enabled, the SGA_TARGET value can be adjusted up to the SGA_MAX_SIZE parameter, not more than SGA_MAX_SIZE parameter value.


you can manage SGA and PGA together rather than managing them separately.

If you set SGA_TARGET, SGA_MAX_SIZE and PGA_AGGREGATE_TARGET to 0 and set MEMORY_TARGET (and optionally MEMORY_MAX_TARGET) to non zero value, Oracle will manage both SGA components and PGA together within the limit specified by you.

If MEMORY_TARGET is set to 1024MB, Oracle will manage SGA and PGA components within itself.

If MEMORY_TARGET is set to non zero value:

  • SGA_TARGET, SGA_MAX_SIZE and PGA_AGGREGATE_TARGET are set to 0, 60% of memory mentioned in MEMORY_TARGET is allocated to SGA and rest 40% is kept for PGA.
  • SGA_TARGET and PGA_AGGREGATE_TARGET are set to non-zero values, these values will be considered minimum values.
  • SGA_TARGET is set to non zero value and PGA_AGGREGATE_TARGET is not set. Still these values will be autotuned and PGA_AGGREGATE_TARGET will be initialized with value of (MEMORY_TARGET-SGA_TARGET).
  • PGA_AGGREGATE_TARGET is set and SGA_TARGET is not set. Still both parameters will be autotunes. SGA_TARGET will be initialized to a value of (MEMORY_TARGET-PGA_AGGREGATE_TARGET).



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