3.Two ways exist to create a combined set of comparable data:

•In one viewer, click File→Compare , or

•click the Compare button .

The Compare window opens, and you can now see the other possible files to compare your first file against.

4.Click the file name that you want to compare against; or, if choosing more than one file, hold the Ctrl key while selecting each desired file.

5.When the files are highlighted, click the Compare button.

A new viewer opens that presents the selected data sets in comparison to one another.

NOTE: For alternate access when you have multiple viewers open, click the button to bring the console to the top. The console lists all open sessions and data sets. For data sets, click the data representation to bring the already open viewer to the top.

If the viewer has been closed, but the data representation is still listed in the console, double-clicking the data representation opens a new viewer.

Basic Garbage Collection Concepts

A basic principle behind the design of the garbage collector is that objects tend to be either short-lived or else persist for the lifetime of an application run. By separating persistent objects from short-lived objects and moving them to designated spaces, the garbage collector can free memory for use by the application (improving efficiency of memory use), and avoid examining every object each time a collection is done (reduce garbage collection overhead).

Through a system of identification and classification, an object ages each time it survives a garbage collection event. After surviving a certain number of garbage collection events, the object is considered old — at which point, it is moved from the young to the old area of the heap.

A scavenge is a garbage collection event where only short-lived, unused objects are collected from the young heap area. Typically, scavenges are significantly faster than a full garbage collection, which involves examining all objects in the entire heap.

Key to Garbage Collection Types Recognized by HPjmeter

HPjmeter reports numerous types of garbage collection. You may see references in HPjmeter to GC types in data summaries or visualizers, so it helps to become familiar with them.

Basic Garbage Collection Concepts

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