The allocation set for any resource provider deletes the previous allocation

Whenever we set a resource provider allocation we have to give some values to a resource class(VCPU, RAM , MEMORY_MB and more). If however we only wish to change one of the resource class then we have to mention the values of previous defined classes because otherwise all the classes that aren't mentioned in new allocation will have no value as every time a new allocation is set all the previous allocations are deleted respective to that resource provider.