I found a very good article on practical uses of Garbage Collection Optimization in J2EE Fine Tuning :-

How We Solved our Garbage Collection Pausing Problem:-

http://gregluck.com/blog/archives/2006/07/how_we_solved_o.html

A detailed explanation about the Garbage Collection can be found at this link :-

http://www-128.ibm.com/developerworks/java/library/j-jtp11253/