Some friend has told me about the meaning about the status of decoupled , here is the explanation about it, for your information.
Basically, in a partitioned database environment, each node performs different tasks quite often. Some node may be executing joins on tables, while other nodes are waiting for the output of the joins. Another node may have finished the task assigned to itself, and stay idle till the end of the transaction.
Hence, on a node, where a db2 agent is executing any task, LIST APPLICATIONS will show it as active. On a node, where no db2 agent is executing any task, itīll show as decoupled. This is the design of the concentrator . An application status of decoupled is possible with or without the concentrator enabled and is nothing to be worried about.