Discussion moved from Business to Security Information and Event Management (SIEM) for better support
Probably the most accurate approximation you're going to get is to ssh into the ESM and type 'free -m'. Look at the number in the free column of the -/+ buffers/cache: row.
total used free shared buffers cached
Mem: 8012 7850 161 0 146 4590
-/+ buffers/cache: 3113 4898
Swap: 4901 73 4828