DCP is uses to logically divide the Array cache. Devices are assigned to a partition and can only use the cache they have been assigned. I can be used to prevent one workload impacting other workloads in the same array.

It is controlled by the SYMQOS cli command. You would only enable it to address a requirement, it is not needed generally.

Yes, as addressed by Jason it needs to be configured for some specific requirement only. refer to symmetrix array control guide for the SYMQOS -cp option