Increasing RF will result in nodes that previously didn't have a replica of the data now being responsible for it. This means that a repair is required after increasing the RF.
Until the repair completes you will suffer from inconsistencies in data. For example, in a 3 node cluster with RF 2, nodes A, B and C. A and B could be responsible for the 2 replicas of row x. As soon as you increase the RF to 3, C will also be responsible for x and thus can also answer queries requesting x. But until row x is repaired and present on C, a request for x against C will return no data. If you are looking to increase RF on a live production system you should perform a datacenter migration and increase the RF to 3 only on the new datacenter, switching your clients across after rebuild+repair on the new DC. allocate_tokens_for_local_replication_factor is a DSE configuration property. allocate_tokens_for_keyspace is the equivalent in Apache Cassandra. This option is not related to RF changes so shouldn't be necessary, however might not be a bad idea to research its usage if you are planning on scaling to many nodes in the future.
