Number of msgs to cache per topic.
Messages are dropped off front of queue once limit is reached.
Use 0 for unlimited but take care not to run out of memory.
Select a context store to use if you have more than one set up.
Use persistent store if you want cache to survive a system reset.
If store changed, old one must be manually deleted.
Select which type of store to use. The default is "Node".
Node = This node's store, only accessible to this node.
Flow/Global = Accessible to other nodes. Use with caution.