Summary

Java disables Compressed Oops for application heaps larger than 32 GB, which changes the memory allocation size from 4 to 8 bytes, reducing the number of objects it can store in the heap. This means that increasing the maximum heap to a value near to 32 GB and up to 47 GB will actually decrease the amount of memory available, leading to possible OutOfMemoryErrors.

Solution

If increasing Jira memory heap size near to, or higher than, 32 GB, set it to >=48 GB and continue adding memory from that point. As a best practice it's also recommended using the same value for Xms and Xmx, this will prevent pauses caused by heap expansion, it also decreases the time garbage collection takes to occur, as it will not attempt to resize the heap down at every cycle. More Information at:

• CompressedOops
• Java Performance Enhancements
• Java GC Tuning Guide
• Additional details about compressed OOPs from the Elastic Search documentation