Storage I/O Control (SIOC) was initially introduced in vSphere 4.1 to provide I/O prioritization and quality of service (QoS) of VM disks running on a cluster with a shared storage. It extended the shares and limits not only at the host level, but at the cluster level. With vSphere 5.0, SIOC provides cluster-wide I/O shares and limits for NFS datastores, not only VMFS datastores.
Objective 3.5 for VCP65-DCV and VCP6-DCV are quite similar just because there weren't big changes in those storage functions from vSphere 6.0 to vSphere 6.5.
For more information and details, see the vSphere 6.5 Storage guide: https://docs.vmware.com/en/VMware-vSphere/6.5/vsphere-esxi-vcenter-server-652-storage-guide.pdf.pdf.
