DRS and load balance

e have few esxi ver5.1.
HA and DRS are enabled. The DRS is set to full automation.
We are monitoring the vm using third party monitoring tool which monitor cpu , memory , dcc using WMI. in the meantime i enabled vcenter alert for esxi host and vms. We get alert for vm and esxi host for memory. I expect the vm to migrate to another esxi host when we get these alerts at 90% or more believing that memory has been taken, but it does not happen. That is, the vm still on a esxi host which is in 90% memory utilization.
1- Why a vm does not get vacated from an exit host which memory almost being used by guest vms?
2- How do i find out a vm goes into balling effect?
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
DRS is not a load balancer, it will only move VMs, when there is pressure on CPU and Memory resources.

Is it set to Aggressive, e.g. slider fully right ?

If you have alerts being triggered for memory in the VM and Host, your host is getting close to out of memory, and your VM is using all it's  memory.

Check the VM, over a few weeks, is this a one off, otherwise increase memory for the VM.

As for Hosts, are all showing alerts ?

Also remember, if all hosts are at 90%, it's unlikely DRS will move any VMs.

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On you vCenter server I you view the drmdump\ directory? It contact all DRS actions and recommendations
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