vSphere DRS is the placement engine that vRealize Automation and vRealize Operations Manager use to provision and place virtual machines.
For vRealize Automation to suggest the best placement for the virtual machines, you must enable DRS on the cluster, and set it to fully automated. vRealize Automation then uses the vSphere DRS APIs to determine the correct placement for the virtual machines.
vRealize Automation integrates with the vRealize Operations Manager placement service. vRealize Operations Manager only provides placement recommendations for clusters that have DRS enabled and fully automated.