partitioned and conveniently reside in the proper processing units in the case of distributing data based on the arrangement of switches in the cluster tables that cannot be replicated on every node can still be replicated among sets of nodes that are connected to a common switch in the cluster processing units connected to a common switch have greater bandwidth for communicating among each other when a join needs to be performed the partitioning and redistribution of data needs to be done only within the set of units connected to the common switch in the case of a cluster having a large number of processing units distributing data based on the switch arrangement is particularly advantageous as mentioned above when the cluster participates in database operations parallelism in the rdbms and transaction consistency are affected because a cluster may be performing significant query processing for the rdbms in one embodiment the rdbms adjusts the number of parallel query processes or threads in accordance with the amount of work the cluster is performing if a join is processed completely in a cluster then each parallel query process or thread handles only the communication with the units in the cluster specifically the rdbms obtains results from the processing units and streams them to other parallel query processes that perform further operations on the query in this case the number of processing units assigned to each process and hence the degree of parallelism depends on the estimated size of the join result and rate at which the processing units are expected.