🚀 Understanding Garbage Collection (GC) Algorithms in WebLogic 🔄

Efficient memory management is crucial for high-performance applications. Garbage Collection (GC) in WebLogic plays a key role in automatically reclaiming unused memory and optimizing application performance. In this blog, we’ll explore different GC algorithms in WebLogic, their use cases, when they were introduced, and how to configure them. 🎯

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🌱 What is Garbage Collection in WebLogic?

Garbage Collection (GC) is the process of automatically identifying and removing unused objects from the JVM heap to free memory. WebLogic uses different GC algorithms to optimize memory management based on workload needs.

🛠️ Key Goals of GC:

• ✅ Free up unused memory to prevent memory leaks.
• ✅ Improve application performance by reducing pause times.
• ✅ Ensure efficient CPU and memory utilization.
• ✅ Minimize stop-the-world events that freeze application threads.

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🔥 Types of Garbage Collection Algorithms in WebLogic

WebLogic supports several GC algorithms, each suited for different workloads. Let’s explore them:

1️⃣ Serial GC 🏎️ (Best for Small Applications) 📅 Introduced in JDK 1.3

✅ Uses a single thread to perform GC. ✅ Suitable for small applications with single CPU cores. ✅ Causes stop-the-world pauses, making it inefficient for high-load systems.

🛠️ Configuration:

-XX:+UseSerialGC

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2️⃣ Parallel GC 🚀 (Best for Multi-Core Systems) 📅 Introduced in JDK 1.4

✅ Uses multiple threads to speed up GC. ✅ Default GC for server-class machines. ✅ Ideal for high-throughput applications.

🛠️ Configuration:

-XX:+UseParallelGC

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3️⃣ G1 GC (Garbage-First) ⚡ (Best for Low Latency) 📅 Introduced in JDK 7

✅ Divides heap into regions for more efficient GC. ✅ Performs incremental garbage collection to reduce pause times. ✅ Ideal for large applications requiring low latency.

🛠️ Configuration:

-XX:+UseG1GC

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4️⃣ ZGC (Z Garbage Collector) 🌍 (Best for Large Memory Applications) 📅 Introduced in JDK 11

✅ Handles heaps up to 16TB efficiently. ✅ Ultra-low pause times, making it perfect for real-time applications. ✅ Ideal for microservices & cloud-native environments.

🛠️ Configuration:

-XX:+UseZGC

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5️⃣ Shenandoah GC 🌊 (Best for Predictable Latency) 📅 Introduced in JDK 12

✅ Performs concurrent GC to reduce pause times. ✅ Designed for low-latency applications. ✅ Ideal for financial & real-time applications.

🛠️ Configuration:

-XX:+UseShenandoahGC

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⚙️ How to Configure GC in WebLogic? 🛠️

✅ Steps to Configure GC in WebLogic Admin Console:

1️⃣ Log in to WebLogic Admin Console. 2️⃣ Navigate to Servers > [Your Server] > Configuration > Server Start. 3️⃣ In Arguments, add the desired GC flag (e.g., -XX:+UseG1GC). 4️⃣ Click Save & Restart the Server for changes to take effect.

🔹 Example: Configuring WebLogic to use G1GC:

-XX:+UseG1GC -Xms2048m -Xmx4096m -XX:MaxGCPauseMillis=200

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🎯 Choosing the Right GC Algorithm

Feature	Serial GC 🏎️	Parallel GC 🚀	G1 GC ⚡	ZGC 🌍	Shenandoah GC 🌊
Introduced In	JDK 1.3	JDK 1.4	JDK 7	JDK 11	JDK 12
Best For	Small Apps	High Throughput	Low Latency	Large Memory Apps	Predictable Latency
Multi-threaded?	❌ No	✅ Yes	✅ Yes	✅ Yes	✅ Yes
Pause Times	⏸️ High	⏸️ Moderate	🔄 Low	🔄 Very Low	🔄 Very Low
Heap Size Support	🟢 Small	🟢 Medium	🔵 Large	🔵 Very Large	🔵 Large
Cloud-Friendly?	❌ No	⚠️ Partially	✅ Yes	✅ Yes	✅ Yes

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🏁 Conclusion

Choosing the right GC algorithm can greatly impact your WebLogic application’s performance, scalability, and responsiveness.

✅ Use Serial GC for small, single-threaded applications. ✅ Use Parallel GC for multi-core high-throughput applications. ✅ Use G1 GC for balancing low latency and high performance. ✅ Use ZGC for ultra-low pause times in large memory applications. ✅ Use Shenandoah GC for real-time applications needing predictable performance.

📌 Pro Tip: Monitor GC performance using JVisualVM or Java Flight Recorder to ensure the best optimization! 📊

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💬 Which GC algorithm do you use in WebLogic? Share your thoughts below! 😊