A survivor region is a young-generation heap region that holds objects remaining reachable after young-generation garbage collections. Objects begin in Eden; survivors move between two survivor areas before eventual promotion to the old generation. section 11.1
This organization helps interpret garbage-collection behavior. Eden is cleaned frequently, survivor regions less often, and objects that remain useful across enough GC cycles move to the old generation. section 11.1
Read survivor-region changes in GC logs by asking:
- Did a young collection move reachable objects out of Eden? section 11.1
- Did the survivor-region count increase, showing that some objects remained alive? section 11.1
- Are objects continuing through survivor areas toward the old generation? section 11.1
Reading one collection
After GC(0), the log reports `Eden regions: 4->0(5)`, `Survivor regions: 0->1(1)`, and `Old regions: 0->0`. Eden was emptied, one survivor region now contains retained objects, and no objects were promoted to the old generation yet. section 11.1
A visual representation of heap memory management illustrates how the heap is structured and how objects are organized based on their life cycle. The heap is divided into multiple regions, where objects are stored according to their age, which is determined by the number of GC cycles they have survived. As objects persist through successive GC cycles, they may be promoted from one region to another, optimizing memory usage and performance.
Use the heap-lifecycle diagram to follow objects as they age through Eden, survivor regions, and the old generation. section 11.1
