The parameter SHMALL is not set properly or, too small.
SHMALL indicates the total amount of shared memory (in pages) that can be used by the system. The default value of SHMALL in Red Hat Enterprise Linux is 2097152 (in pages). If PAGE_SIZE is 4096 bytes, this value (2097152) indicates that, 8 GB of shared memory is available to the system. So for this setup, to avoid ORA-27102, you must tune the values of SHMALL and SHMMAX with the increase in the total SGA of the system over 8 GB.