Ad Hoc cache limit in version 5.6

Issue:

Beginning with JasperReports Server v5.0, the property maxBytesLocalHeap was added to adhoc-ehcache.xml to limit the size of in-memory Ad Hoc cache so that it does not grow to consume the entire heap. But the limit was never enforced until JasperReports Server v5.6. By default the limit is set to 300 MB.

There is a potential performance issue here because once the limit is reached, as new items are added to the cache the oldest items are evicted. Constantly updating the cache creates a great deal of overhead. 

Resolution:

Edit WEB-INF/adhoc-ehcache.xml and set the value for maxBytesLocalHeap to be at least half of your heap size. So, if you have your heap size set to -Xmx4048m then set maxBytesLocalHeap=2024m.