Sometimes Job randomly have an OutOfMemoryError:

FATAL: GC overhead limit exceeded
java.lang.OutOfMemoryError: GC overhead limit exceeded

You can see in the enclosed report that most of the space is taken by String.
I look deeper and the String are log but some of thems are some quite old and it happenned even when I have only one job running.

info on this kind of error from sun page (http://java.sun.com/javase/technologies/hotspot/gc/gc_tuning_6.html#par_gc.oom):

The concurrent collector will throw an OutOfMemoryError if too much time is being spent in garbage collection: if more than 98% of the total time is spent in garbage collection and less than 2% of the heap is recovered, an OutOfMemoryError will be thrown. This feature is designed to prevent applications from running for an extended period of time while making little or no progress because the heap is too small. If necessary, this feature can be disabled by adding the option -XX:-UseGCOverheadLimit to the command line.