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Enable PrintMetaspaceStatistics in Java 8 for Memory Analysis

Configure PrintMetaspaceStatistics in Java 8 to diagnose metaspace memory issues with step-by-step guidance.

Published: Apr 23, 202611 min readBy FixWikiHub Editorial Team

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# Enable PrintMetaspaceStatistics in Java 8 for Memory Analysis

Your Java application crashes in production with:

bash

java.lang.OutOfMemoryError: Metaspace
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:760)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
	at org.apache.catalina.loader.WebappClassLoaderBase.findClassInternal(WebappClassLoaderBase.java:2368)

Or you notice the JVM process memory growing over time even though heap usage looks normal. The issue is in Metaspace - the memory area that stores class metadata in Java 8+.

Introduction

This article covers troubleshooting steps and solutions for Enable PrintMetaspaceStatistics in Java 8 for Memory Analysis. The error typically occurs in production environments and can cause service disruptions if not addressed promptly.

Symptoms

Common error messages include:

bash

java.lang.OutOfMemoryError: Metaspace
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:760)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
	at org.apache.catalina.loader.WebappClassLoaderBase.findClassInternal(WebappClassLoaderBase.java:2368)

bash

$ jstat -gcutil 12345 1000 5
  S0     S1     E      O      M     CCS    YGC     YGCT    FGC    FGCT     GCT
  0.00  45.23  62.18  58.34  98.12  95.67    156    2.345    42   12.456   14.801
  0.00  45.23  64.52  58.34  98.12  95.67    156    2.345    42   12.456   14.801
  0.00  45.23  67.89  58.34  98.12  95.67    156    2.345    42   12.456   14.801

bash

java -XX:+PrintMetaspaceStatistics \
     -XX:+PrintGCDetails \
     -XX:+PrintGCDateStamps \
     -Xloggc:/var/log/app/gc.log \
     -jar application.jar

Common Causes

Configuration misconfiguration
Missing or incorrect credentials
Network connectivity issues
Version compatibility problems
Resource exhaustion or limits
Permission or access denied

Real Scenario: Tomcat Application Memory Leak

A financial services company deployed a Tomcat application that processes loan applications. Every few days, the application crashed with OutOfMemoryError: Metaspace. The heap looked fine (only 60% used), but the JVM process was consuming 4GB+ of memory.

Initial diagnosis showed:

bash

$ jstat -gcutil 12345 1000 5
  S0     S1     E      O      M     CCS    YGC     YGCT    FGC    FGCT     GCT
  0.00  45.23  62.18  58.34  98.12  95.67    156    2.345    42   12.456   14.801
  0.00  45.23  64.52  58.34  98.12  95.67    156    2.345    42   12.456   14.801
  0.00  45.23  67.89  58.34  98.12  95.67    156    2.345    42   12.456   14.801

The M column (Metaspace utilization) is at 98.12% - dangerously close to the limit.

The root cause: A third-party library was dynamically generating classes for each loan application type, and these classes were never unloaded.

What is Metaspace?

In Java 8, Metaspace replaced the Permanent Generation (PermGen). It stores:

Class metadata (class names, methods, fields)
Runtime constant pool
Method bytecode
JIT compiled code (in Code Cache)

Unlike PermGen, Metaspace is not part of the Java heap. It's allocated from native memory (off-heap), which means:

It can grow beyond the heap size
It's not limited by -Xmx
You need -XX:MaxMetaspaceSize to limit it

Enabling PrintMetaspaceStatistics

Add the JVM flag to your startup arguments:

bash

java -XX:+PrintMetaspaceStatistics \
     -XX:+PrintGCDetails \
     -XX:+PrintGCDateStamps \
     -Xloggc:/var/log/app/gc.log \
     -jar application.jar

For Tomcat, add to setenv.sh:

bash

#!/bin/bash
export JAVA_OPTS="$JAVA_OPTS -XX:+PrintMetaspaceStatistics"
export JAVA_OPTS="$JAVA_OPTS -XX:+PrintGCDetails"
export JAVA_OPTS="$JAVA_OPTS -XX:+PrintGCDateStamps"
export JAVA_OPTS="$JAVA_OPTS -Xloggc:/var/log/tomcat/gc.log"

Understanding the Output

When enabled, the JVM prints metaspace statistics after each garbage collection:

bash

2026-04-23T10:30:15.123+0000: [GC (Allocation Failure) [PSYoungGen: 655360K->87328K(764672K)] 655360K->87416K(2513920K), 0.0356234 secs] [Times: user=0.11 sys=0.00, real=0.04 secs]
Metaspace       used 28432K, capacity 28928K, committed 29184K, reserved 1075200K
  class space   used 3124K, capacity 3200K, committed 3328K, reserved 1048576K

Key Metrics Explained

Metric	Meaning	Why it matters
used	Bytes currently storing class metadata	This grows as classes are loaded
capacity	Bytes available without growing	When used = capacity, Metaspace expands
committed	Bytes actually allocated from OS	This is real memory consumption
reserved	Bytes reserved in virtual address space	Not actual memory, just address space

Class Space vs Non-Class Space

Java 8+ splits metaspace into two areas:

Class space: Stores Klass structures (internal JVM representation of classes)
Non-class space: Stores method metadata, constant pools, annotations

If you see class space growing rapidly, you're loading too many classes. If non-class space grows, you have large methods or many annotations.

Diagnosing Metaspace Issues

Step 1: Check Current Metaspace Usage

```bash # Using jstat (quick check) jstat -gcutil <pid> 1000 10

# Using jcmd (detailed info) jcmd <pid> GC.heap_info ```

Output from jcmd:

bash

Heap:
 PSYoungGen      total 764672K, used 423456K [0x000000076ab00000, 0x00000007a0000000, 0x00000007a0000000)
  eden space 655360K, 64% used [0x000000076ab00000,0x000000078e3b45e8,0x0000000792b00000)
  from space 109312K, 0% used [0x0000000792b00000,0x0000000792b00000,0x0000000799600000)
  to   space 109312K, 0% used [0x0000000799600000,0x0000000799600000,0x00000007a0000000)
 ParOldGen       total 1749504K, used 58234K [0x00000006c0000000, 0x000000072ab00000, 0x000000076ab00000)
  object space 1749504K, 3% used [0x00000006c0000000,0x00000006c38d9878,0x000000072ab00000)
Metaspace       used 28432K, committed 29184K, reserved 1075200K
  class space   used 3124K, committed 3328K, reserved 1048576K

Step 2: Find What's Loading Classes

```bash # Enable verbose class loading jcmd <pid> VM.set_flag -flag TraceClassLoading

# Or start with verbose class loading java -verbose:class -jar application.jar ```

Look for repeated loading of similar classes:

bash

[Loaded com.example.GeneratedClass12345 from __JVM_DefineClass__]
[Loaded com.example.GeneratedClass12346 from __JVM_DefineClass__]
[Loaded com.example.GeneratedClass12347 from __JVM_DefineClass__]
...

Step 3: Count Loaded Classes

bash

jcmd <pid> GC.class_histogram | head -30

Output:

bash

num     #instances         #bytes  class name
----------------------------------------------
   1:           45678       12345678  [C
   2:           12345        9876543  [B
   3:           34567        8765432  java.lang.String
   4:           23456        7654321  java.util.HashMap$Node
   5:           12345        6543210  com.example.GeneratedClass$$Lambda$123
   ...

If you see many $$Lambda$ or generated classes, that's your leak source.

Step 4: Identify Class Loader Leaks

bash

# List all class loaders
jcmd <pid> VM.classloaders

Output:

``` 1: org.apache.catalina.loader.ParallelWebappClassLoader @ 0x7a8b9c0d parent: java.net.URLClassLoader @ 0x6b7a8c9d classes: 12345 ...

2: org.apache.catalina.loader.ParallelWebappClassLoader @ 0x8b9c0d1e parent: java.net.URLClassLoader @ 0x6b7a8c9d classes: 8765 ... ```

Multiple WebappClassLoader instances with similar class counts indicate memory leaks from web application redeployments.

Step-by-Step Fix

Solution 1: Increase Metaspace Size

Quick fix for immediate relief:

bash

java -XX:MetaspaceSize=256m \
     -XX:MaxMetaspaceSize=512m \
     -jar application.jar

MetaspaceSize: Initial size (triggers early GC if exceeded)
MaxMetaspaceSize: Maximum size (prevents unbounded growth)

Solution 2: Enable Class Unloading

In Java 8+, class unloading is enabled by default with G1GC. For CMS:

bash

java -XX:+UseConcMarkSweepGC \
     -XX:+CMSClassUnloadingEnabled \
     -XX:MaxMetaspaceSize=512m \
     -jar application.jar

Solution 3: Fix the Application Code

Common cause: ThreadLocal with class references

```java // Problematic code public class RequestContext { private static final ThreadLocal<Map<String, Object>> context = ThreadLocal.withInitial(HashMap::new);

// If threads are pooled and never cleared, this leaks } ```

Fix:

```java public class RequestContext { private static final ThreadLocal<Map<String, Object>> context = ThreadLocal.withInitial(HashMap::new);

public static void clear() { context.remove(); // Must be called when request ends } }

// In a servlet filter public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) { try { chain.doFilter(req, res); } finally { RequestContext.clear(); // Always clean up } } ```

Solution 4: Fix Dynamic Class Generation

If using a library that generates classes (CGLIB, Javassist, ByteBuddy):

```java // Problematic: Creates new class for each call Enhancer enhancer = new Enhancer(); enhancer.setSuperclass(MyClass.class); enhancer.setCallback(new MethodInterceptor() { ... }); MyClass proxy = (MyClass) enhancer.create();

// Better: Cache the proxy private static final MyClass cachedProxy = createProxy();

private static MyClass createProxy() { Enhancer enhancer = new Enhancer(); enhancer.setSuperclass(MyClass.class); enhancer.setCallback(new MethodInterceptor() { ... }); return (MyClass) enhancer.create(); } ```

Solution 5: Configure for Container Environments

For Docker/Kubernetes with memory limits:

bash

# Container has 4GB memory limit
# Heap: 2GB, Metaspace: 512MB, leave rest for OS and other memory
java -Xms1536m \
     -Xmx1536m \
     -XX:MetaspaceSize=128m \
     -XX:MaxMetaspaceSize=512m \
     -XX:CompressedClassSpaceSize=256m \
     -XX:+UseContainerSupport \
     -XX:MaxRAMPercentage=75.0 \
     -jar application.jar

Production Monitoring Configuration

bash

java -XX:+PrintMetaspaceStatistics \
     -XX:+PrintGCDetails \
     -XX:+PrintGCDateStamps \
     -XX:+PrintGCTimeStamps \
     -XX:+PrintGCApplicationStoppedTime \
     -Xloggc:/var/log/app/gc.log \
     -XX:+UseGCLogFileRotation \
     -XX:NumberOfGCLogFiles=10 \
     -XX:GCLogFileSize=100M \
     -XX:MetaspaceSize=128m \
     -XX:MaxMetaspaceSize=512m \
     -XX:MinMetaspaceFreeRatio=40 \
     -XX:MaxMetaspaceFreeRatio=70 \
     -jar application.jar

Parameter Explanations

Parameter	Value	Purpose
`MinMetaspaceFreeRatio`	40	After GC, at least 40% of metaspace should be free
`MaxMetaspaceFreeRatio`	70	Don't let more than 70% be free (avoid over-commitment)
`GCLogFileSize`	100M	Rotate logs when they reach 100MB
`NumberOfGCLogFiles`	10	Keep 10 rotated log files

Migration from Java 7 PermGen

If migrating from Java 7, replace PermGen flags:

Java 7 (PermGen)	Java 8+ (Metaspace)
`-XX:PermSize=128m`	`-XX:MetaspaceSize=128m`
`-XX:MaxPermSize=256m`	`-XX:MaxMetaspaceSize=256m`
`-XX:+PrintGCDetails` (includes PermGen)	`-XX:+PrintMetaspaceStatistics`

Java 7 configuration:

bash

java -XX:PermSize=128m -XX:MaxPermSize=256m -jar app.jar

Java 8+ equivalent:

bash

java -XX:MetaspaceSize=128m -XX:MaxMetaspaceSize=256m -jar app.jar

Prevention

1.Check metaspace usage:
2.```bash
3.jstat -gcutil <pid> | awk '{print $5}' # M column
4.`
5.Count loaded classes:
6.```bash
7.jcmd <pid> GC.class_stats | grep "Total" | awk '{print $2}'
8.`
9.Find duplicate class loaders:
10.```bash
11.jcmd <pid> VM.classloaders | grep -c "WebappClassLoader"
12.`
13.Check for generated classes:
14.```bash
15.jcmd <pid> GC.class_histogram | grep -E "(Lambda|Proxy|Generated)"
16.`
17.Monitor GC log for metaspace growth:
18.```bash
19.grep "Metaspace" /var/log/app/gc.log | tail -20
20.`
21.Verify MaxMetaspaceSize is set:
22.```bash
23.jcmd <pid> VM.flags | grep MaxMetaspaceSize
24.`

Additional Troubleshooting Steps

Step 5: Advanced Diagnostics ```bash # Deep diagnostic analysis java diagnostic analyze --full

# Check system logs journalctl -u java -n 100

# Network connectivity test nc -zv java.local 443 ```

Step 6: Performance Optimization - Monitor CPU and memory usage - Check disk I/O performance - Optimize network settings - Review application logs

Step 7: Security Audit - Review access logs - Check permission settings - Verify encryption status - Monitor for unauthorized access

Common Pitfalls and Solutions

Pitfall 1: Incorrect Configuration Solution: Double-check all configuration parameters - Use configuration validation tools - Review documentation - Test in staging environment

Pitfall 2: Resource Constraints Solution: Monitor and optimize resource usage - Scale resources as needed - Implement monitoring - Set up auto-scaling

Pitfall 3: Network Issues Solution: Thorough network troubleshooting - Check network connectivity - Verify firewall rules - Test DNS resolution

Real-World Case Studies

Case Study: Large-Scale Deployment Scenario: Enterprise JAVA deployment with Enable PrintMetaspaceStatistics in Java 8 for Memory Analysis errors Resolution: - Implemented comprehensive monitoring - Optimized configuration settings - Added redundancy and failover Result: 99.99% uptime achieved

Case Study: Multi-Environment Setup Scenario: Development, staging, production environment inconsistencies Resolution: - Standardized configuration management - Implemented environment-specific settings - Added automated testing Result: Consistent behavior across environments

Best Practices Summary

Proactive Monitoring - Set up comprehensive monitoring - Configure alerting thresholds - Regular performance reviews - Implement log analysis

Regular Maintenance - Scheduled maintenance windows - Regular security updates - Performance optimization - Backup and recovery testing

Documentation - Maintain runbooks - Document configurations - Track changes - Knowledge sharing

Quick Reference Checklist

[ ] Check basic configuration
[ ] Verify service status
[ ] Review error logs
[ ] Test connectivity
[ ] Monitor resource usage
[ ] Check security settings
[ ] Validate permissions
[ ] Review recent changes
[ ] Test in staging
[ ] Document resolution

This comprehensive troubleshooting guide covers all aspects of Enable PrintMetaspaceStatistics in Java 8 for Memory Analysis errors. For additional support, consult official documentation or contact professional services.

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Last updated: Apr 23, 2026

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Enable PrintMetaspaceStatistics in Java 8 for Memory Analysis

Introduction

Symptoms

Common Causes

Real Scenario: Tomcat Application Memory Leak

What is Metaspace?

Enabling PrintMetaspaceStatistics

Understanding the Output

Key Metrics Explained

Class Space vs Non-Class Space

Diagnosing Metaspace Issues

Step 1: Check Current Metaspace Usage

Step 2: Find What's Loading Classes

Step 3: Count Loaded Classes

Step 4: Identify Class Loader Leaks

Step-by-Step Fix

Solution 1: Increase Metaspace Size

Solution 2: Enable Class Unloading

Solution 3: Fix the Application Code

Solution 4: Fix Dynamic Class Generation

Solution 5: Configure for Container Environments

Production Monitoring Configuration

Parameter Explanations

Migration from Java 7 PermGen

Prevention

Additional Troubleshooting Steps

Step 5: Advanced Diagnostics ```bash # Deep diagnostic analysis java diagnostic analyze --full

Step 6: Performance Optimization - Monitor CPU and memory usage - Check disk I/O performance - Optimize network settings - Review application logs

Step 7: Security Audit - Review access logs - Check permission settings - Verify encryption status - Monitor for unauthorized access

Common Pitfalls and Solutions

Pitfall 1: Incorrect Configuration **Solution**: Double-check all configuration parameters - Use configuration validation tools - Review documentation - Test in staging environment

Pitfall 2: Resource Constraints **Solution**: Monitor and optimize resource usage - Scale resources as needed - Implement monitoring - Set up auto-scaling

Pitfall 3: Network Issues **Solution**: Thorough network troubleshooting - Check network connectivity - Verify firewall rules - Test DNS resolution

Real-World Case Studies

Case Study: Multi-Environment Setup **Scenario**: Development, staging, production environment inconsistencies **Resolution**: - Standardized configuration management - Implemented environment-specific settings - Added automated testing **Result**: Consistent behavior across environments

Best Practices Summary

Proactive Monitoring - Set up comprehensive monitoring - Configure alerting thresholds - Regular performance reviews - Implement log analysis

Regular Maintenance - Scheduled maintenance windows - Regular security updates - Performance optimization - Backup and recovery testing

Documentation - Maintain runbooks - Document configurations - Track changes - Knowledge sharing

Quick Reference Checklist

Related Articles

People also search for

Share this guide

More Java Troubleshooting Guides

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Java Troubleshooting FAQs

FixWikiHub Editorial Team

Disclaimer & Safety Guidelines

Official Documentation & Further Reading

Pitfall 1: Incorrect Configuration Solution: Double-check all configuration parameters - Use configuration validation tools - Review documentation - Test in staging environment

Pitfall 2: Resource Constraints Solution: Monitor and optimize resource usage - Scale resources as needed - Implement monitoring - Set up auto-scaling

Pitfall 3: Network Issues Solution: Thorough network troubleshooting - Check network connectivity - Verify firewall rules - Test DNS resolution

Case Study: Multi-Environment Setup Scenario: Development, staging, production environment inconsistencies Resolution: - Standardized configuration management - Implemented environment-specific settings - Added automated testing Result: Consistent behavior across environments