Increasing MEMORY_MAX_TARGET - 11.2.0.3 and /dev/shm

Hi

In our 11.2.0.3 RAC database, we have the following memory settings

memory_max_target                    big integer 6368M
    memory_target                        big integer 6368M

SQL> show sga

Total System Global Area 2772574208 bytes
Fixed Size                  2229720 bytes
Variable Size            2684357160 bytes
Database Buffers           67108864 bytes
Redo Buffers               18878464 byte

We are recently getting ORA-04031 errors related shared pool so we are thinking of increasing the MEMORY_MAX_TARGET to 10GB (from 6 GB)

Here is our /dev/shm setting

SQL> host df -m |grep tmpfs

tmpfs                     7960      2847      5114  36% /dev/shm


2 questions:

1. How come we have the memory_max_target set to 6 GB but show sga shows the SGA to be 2.7 GB (does it mean that the rest of the memory 6GB  - 2.7 GB = 2.3 GB is allocated to other likes PGA etc?