MySQL eats up all the memory from the RHEL OS
9 times out of 10 this is due to a hungry query. Set long-query-time to something &lt; 2 and once you have a good sample size analyse the log file using the Percona tool pt-query-digest. This should give you a good place to start. 

Try splitting your transactional and analytical workloads. Running them on different hardware is common place.