Clicking on this box will expand the tree of references rightward, assuming there are further references. A blue upward-pointing arrow identifies a repetition of the same node. Clicking on this arrow will produce a long blue arrow leading to another occurrence of the same node. Old-generation objects are those created prior to a certain point in the trace . You can specify that point as you're taking the trace using the dump population tracing command.
Objects created after that point are new-generation objects.
A small circle appearing to the left of a node indicates that this object is referred to by a source other than a Java object. You may select an object or a group of objects by left-clicking on the appropriate node. Nodes will be highlighted in yellow if at least one of the objects represented by the node is currently selected in any view. Menus Popup menus. The enumerated object information includes the instance number, the time the object was reported, and the number of bytes of memory it consumes.