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JVM Heap Memory Monitoring

The JVM Heap is where objects and data are allocated at runtime. If objects are not released by the application, heap usage grows. We monitor Garbage Collection (GC) activity and heap usage to detect memory issues and prevent OutOfMemoryError (OOM).

Heap Used
1.62 GB (54.1%)
of 3.00 GB
5.6% vs last 1 hour
Heap Committed
2.10 GB
of 3.50 GB
No Change
Heap Max
3.50 GB
Max Configured Heap
No Change
JVM Memory Usage
54.1%
Used 1.62 GB
Free 1.38 GB
Max 3.00 GB
Heap Usage Trend (Last 1 Hour)
Heap Used
Heap Committed
3.0 GB2.0 GB1.0 GB0 GB
10:00 AM10:10 AM10:20 AM10:30 AM10:40 AM10:50 AM11:00 AM
What Does This Graph Indicate?
  • Sawtooth Pattern: Indicates healthy GC. Heap usage rises as objects are created and drops after GC.
  • Increasing Trend / No Drop: Indicates memory leak or GC not able to reclaim memory.
  • Consistent High Usage: Risk of OOM if reaches close to Max Heap.
GC Frequency
Monitor Spikes
18
times / hour
12% vs last 1 hour
GC Pause Times
< 50 ms
Max: 42 ms | Avg: 18 ms
Healthy
Recommended: < 50 ms
GC Details (Last 1 Hour)
GC Type Count Avg Pause (ms) Max Pause (ms) Total Pause Time (ms)
Young GC (Minor) 15 12 28 180
Full GC (Major) 3 120 210 360
Concurrent Mark Sweep 0 0 0 0
What Do These Metrics Mean?
  • GC Frequency: Number of times GC occurred. High frequency may indicate memory pressure.
  • GC Pause Times: Time taken to pause application threads during GC. High pause times can impact performance.
  • Healthy Systems: Low GC frequency with low pause times.
Understanding JVM Heap Memory
Heap Used
Memory currently used by objects in the heap.
  • If this keeps increasing and never drops, it indicates a memory leak.
  • Consistently high usage (>85%) increases the risk of Full GC and OOM.
Heap Committed
Memory that JVM has requested from the operating system for the heap.
  • This is the actual memory reserved for the heap and is <= Heap Max.
Heap Max
Maximum heap size configured for the JVM using -Xmx parameter.
  • Setting too low may cause OOM.
  • Setting too high can cause longer GC pauses.
Garbage Collection (GC)
JVM automatically reclaims memory from objects that are no longer in use.
  • Young GC (Minor): Collects short-lived objects in Eden space.
  • Full GC (Major): Collects all objects in the heap. Occurs less frequently but takes longer.
Why It Matters
Improper memory management leads to:
  • High GC frequency → More CPU usage.
  • Long GC pause times → Poor response time.
  • Continuous heap growth → OutOfMemoryError (OOM) → Application crash.

How to Identify JVM Memory Issues – Analysis Steps

1
Check Heap Usage Trend
Look for sawtooth pattern. Healthy: Regular ups and downs. Issue: Continuous rise or consistently high usage.
2
Analyze GC Frequency
Low to moderate GC frequency is normal. Issue: Very high frequency indicates memory pressure or leak.
3
Review GC Pause Times
Check Avg and Max pause times. Issue: High pause times cause slow application response.
4
Check GC Types
If Full GC occurs frequently, it means heap is not able to reclaim memory in Minor GC. Issue: Frequent Full GC is critical.
5
Correlate with Application Issues
Match memory spikes or high pause times with slow transactions or errors in application.
6
Take Action
Tune JVM or fix memory leak in application.

Re-monitor to confirm improvement.

Common JVM Memory Issues and Recommendations

Issue Symptoms Possible Cause Recommended Action
Memory Leak
 Heap used continuously increases and never drops. Objects are not released by application. Use heap dump analysis (MAT, VisualVM) to find leak.
Fix code to release unused objects.
High GC Frequency
 Too many GC cycles in short time. Small heap size or memory leak. Increase heap size (-Xmx).
Optimize code to reduce object creation.
High GC Pause Time
 Application response time is slow. Large heap or too many objects to GC. Tune heap size.
Use G1GC or CMS for better performance.
OutOfMemoryError (OOM)
 Application crashes with OOM. Heap size insufficient or memory leak. Increase heap size.
Fix memory leak in application.

Best Practices for JVM Heap Memory Management

Set appropriate heap size using -Xms and -Xmx.

Monitor heap usage trend regularly.

Keep GC pause times < 50ms.

Use G1GC for better performance.

Analyze heap dumps periodically.

Fix memory leaks proactively.

Proper JVM heap monitoring ensures application stability, optimal performance, and prevents OutOfMemoryError (OOM).