How to enable the garbage collection trace facilities on IBM Java 2 SDK 1.4.1
 Technote (FAQ)
 
Problem
This document describes how to enable the garbage collection trace facilities on Java™ SDK 1.4.1.
 
 
Solution
From IBM® Java 2 SDK version 1.4.1, garbage collection trace options (previously known as tracegc) have been merged with the JVM RAS trace, and the -Xtgc option is no longer used. Therefore, although the information that is available from this trace remains mostly unchanged, usage of the trace has changed.

In 1.4.1, the -Xtgc functionality is achieved by using -Dibm.dg.trc.print

For example, you can use the following in 1.4.1:

1.3.1 1.4.1
-Xtgc2 -Dibm.dg.trc.print=st_verify
-Xtgc34 -Dibm.dg.trc.print=st_compact_verbose,st_verify

Here is the list of available traces:

st_terse Dumps the contents of the heap before and after a garbage collection.
st_verify Verifies the integrity of the heap before and after a compaction.
st_mark Traces all the objects that are found during the conservative part of marking.
st_compact Traces all the moves that occur during a compaction.
st_compact_verbose Runs only with st_verify; shows all the pinned and dosed objects that are on the heap before a compaction.
st_compact_dump Runs only with st_verify; dumps the contents of the heap before a compaction and after a compaction.
st_dump Runs only with st_verify; displays every free chunk that is in the heap, including dark matter (free chunks that are too small to be on the free list). If it runs with the -Xresettable option, the transient-heap free chunks are also displayed.
st_alloc Traces every heap lock allocation.
st_refs Traces reference handling during garbage collection.
st_backtrace Runs only with st_terse; adds one line to the beginning of the st_terse trace. This shows the name of the thread that is running garbage collection, followed by the address of the sys_thread_t structure.
st_freelist Traces information about the freelist during garbage collection.
st_calloc Traces successful calls to realObjCalloc() and transientRealObjCalloc().
st_parallel Traces the activity of parallel mark and parallel sweep, producing some statistics.
st_trace Traces all the work that is done by the mark phase.
st_concurrent Traces the state of WorkPackets that are in concurrent mark.
st_concurrent_pck Traces frequent operations on WorkPackets, such as getting, or returning.
st_icompact Traces, by an incremental compaction, all the work that has been done.
st_concurrent_shadow_heap To use this trace, you must also be running the debug build.
 
 


Document Information


Product categories: Software > Application Servers > Distributed Application & Web Servers > WebSphere Application Server > Java SDK
Operating system(s): Windows
Software version: 6.0
Software edition:
Reference #: 1172922
IBM Group: Software Group
Modified date: Jun 25, 2004