Rather than removing the entries from the database, download the VMware Cloud Client 4.
Run the batch from a server with access to both the vRA and IaaS server.
First you need to login to your vRA Server
vra login userpass –user <user> –password <password> –server <vRA Server> –tenant <Tenant>
To test that you are connected correctly, you could for example retrieve a list of catalog items
vra catalog list
Next, login to the IaaS Server
vra login iaas –server <IaaS Model Manager> –domain <domain> –user <user> –password <password>
Now get rid of those annoying machines
vra machines forceunregister –name <Managed Machine Name>
That is it … now wait a few minutes and refresh the list of machines and you should see that those are dead and gone now.
Note: It only removes them from vRA but leaves the actual VMs alone.