You can disable HA & DRS for specific VMs,
To disable DRS
Navigate to the edit settings of the cluster then click on vSphere DRS > Virtual Machine Options > Select Disabled for the specific Oracle VMs.
To disable HA
Navigate to the edit settings of the cluster then click on vSphere HA > Virtual Machine Options > Disable VM Restart Priority, this will disable HA for that specific VM. Also you can configure the Host Isolation Response to leave Powered On.
--Arun