Workaround 1:-This error indicates that the SGA is large for the amount of shared memory you have allocated in /etc/system file.
While creating database you may have to decrease the db_block_buffers. Please use the below formula to calculate SGA size.
sga size = db_block_buffers* block_size + shared_pool * log_buffer
Please note that when you are increasing your block size, try to reduce the value of db_block_buffers in your init.ora file.
This is just a work around and you may need to increase the max shared memory limit on the server. If this won’t work try "workaround 2".
Workaround 2:- Increase the kernel parameter shell limits.
Please see the below link for recommended values and make sure that the kernel parameter values should be greater than or equal to recommended values. http://download.oracle.com/docs/cd/B19306_01/install.102/b15704/pre_install.htm#sthref258
Click here to see How to resolve ORA-27102 error on Linux.