A customer Java application is running with these setting:
Java version: 1.4.2_06-b03
MAX_HEAP_SIZE=3072
FILE_DESC_LIMIT=1024
CURR_DATE=`date "+%Y%m%d%H%M%S"`
JAVA_HOME=../Shared/jre
JRE_PARAMS=" -d64 -Djava.library.path=../Shared -Xmx${MAX_HEAP_SIZE}m -DMaxHeapMemory=${MAX_HEAP_SIZE} -Xloggc:/xacct5/Gatherer3/G3/Log/IPM_G3_GC_${CURR_DATE}.txt -verbose:gc -XX:+PrintGCTimeStamps -XX:+PrintGCDetails -XX:+PrintGCApplicationStoppedTime"

About once a day, application threads are stopped for extremely long time, while collections themsleves are reported to take much less time. For example:
---------------------------------
289819.725: [GC 289819.726: [DefNew: 675904K->20480K(675904K), 2.1701343 secs] 1685692K->1139971K(2066768K), 2.1707716 secs]
Total time for which application threads were stopped: 48.8805907 seconds
---------------------------------
Changed synopsis from:

Application threads stop time during GC is much greater than actual collections

to:

Application threads stopped for much longer than garbage collection time