30.3. Setting Shared Memory

For Oracle9i installations, the maximum shared memory size must be increased. If it is too small, the Oracle Database Configuration Assistant will display the following error message: 
ORA-27123: unable to attach to shared memory segment.
To increase the shmmax setting, execute the following command: 
$ su - root
# cat /proc/sys/kernel/shmmax
33554432
# echo `expr 1024 \* 1024 \* 1024` > /proc/sys/kernel/shmmax
# cat /proc/sys/kernel/shmmax
1073741824
It is recommended to increase the shmmax setting permanently for Oracle. For more information on optimizing shared memory settings for Oracle databases on Linux, see Chapter 7, Setting Shared Memory. These parameters apply to all Red Hat Enterprise Linux versions.