Resolution:
Here is a list of variable that control the heap dump behaviour of a JVM on AIX box.

Environment variables used to produce heap dumps

IBM_HEAPDUMP or IBM_HEAP_DUMP  
Setting either of these to any value (such as true) enables heap dump production by means of signals.  

IBM_HEAPDUMPDIR  
The default location into which the Heapdump will be written.  

JAVA_DUMP_OPTS  
Use this environment variable to control the conditions under which Heapdumps (and other dumps) are produced. See Using Heapdump for more information .  

IBM_HEAPDUMP_OUTOFMEMORY  
By setting this environment variable to false, you disable Heapdumps for an OutOfMemory condition.  

IBM_JAVA_HEAPDUMP_TEST  
Use this environment variable to cause the JVM to generate both phd and text versions of Heapdumps. Equivalent to opts=PHD+CLASSIC on the -Xdump:heap option.  

IBM_JAVA_HEAPDUMP_TEXT  
Use this environment variable to cause the JVM to generate a text (human readable) Heapdump. Equivalent to opts=CLASSIC on the -Xdump:heap option.


For more details on heap dump on AIX, please refer to the below link

http://publib.boulder.ibm.com/infocenter/javasdk/v5r0/index.jsp?topic=/com.ibm.java.doc.diagnostics.50/html/heapdump.html

KEYWORDS: IBM AIX HEAPDUMP HEAP DUMP