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Manual memory management is time consuming, and error prone. Most programs still contain leaks. This is all doubly true with programs using exception-handling and/or threads. Garbage collection (GC) is a part of WebLogic's JVM, that automatically determines what memory a program is no longer using, and recycles it for other use. It is also known as "automatic storage (or memory) reclamation''.

The JVMGCTest reports the performance statistics pertaining to the JVM's garbage collection. The measures generated by this test are:

Measurement	Description	Measurement Unit	Interpretation
Number_of_GC	The number of times garbage collection has happened	Number	If adequate memory is not allotted to the JVM, then the value of this measure would be very high. A high value of this measure is indicative of a high frequency of GC. This is not a good sign, as GC, during its execution, has the tendency of suspending an application, and a high frequency of GC would only adversely impact the application's performance. To avoid this, it is recommended that you allot sufficient memory to the JVM.
Total_GC_time	The sum of the time taken by all garbage collections	Secs	If adequate memory is not allotted to the JVM, then the value of this measure would be very high. This is not a good sign, as GC, during its execution, has the tendency of suspending an application, and a high value of this measure would only adversely impact the application's performance. To avoid this, it is recommended that you allot sufficient memory to the JVM.
Avg_GC_frequency	The frequency with which the JVM performed GC	Secs	If adequate memory is not allotted to the JVM, then the value of this measure would be very low. A low value of this measure is indicative of a high frequency of GC. This is not a good sign, as GC, during its execution, has the tendency of suspending an application, and a high frequency of GC would only adversely impact the application's performance. To avoid this, it is recommended that you allot sufficient memory to the JVM.
Avg_GC_pause	The average time the application is suspended while garbage collection is in progress	Sec/GC	If the garbage collection takes more time to complete, then it indicates a very high memory allocation to the JVM. This again hinders application performance.
Avg_GC_overhead	The percentage of time utilized by the JVM for garbage collection	Percent	By carefully examining the application behavior in terms of memory utilization, you should arrive at an optimal ratio of the number of times the GC needs to run and how long it should take to complete. Accordingly, memory allocation to the JVM can be performed.
Max_GC_pause	The maximum time spent by the JVM on garbage collection, during the last measurement period	Sec
Avg_heap_before_GC	The average heap size prior to garbage collection	KB
Avg_heap_after_GC	The average heap size after garbage collection	KB	The difference between the value of this measure and the Avg_heap_before_GC measure provides the amount of memory that has been released by GC. This value is a good indicator of the effectiveness of GC.