java

name

java

description

Monitor Java Virtual Machines running on IBM i including heap memory usage, garbage collection activity, thread counts, and JVM configuration. Use when user asks about: (1) active JVMs on the system, (2) JVM heap or memory consumption, (3) garbage collection performance, (4) Java thread counts, (5) JVM home directories or properties, (6) identifying JVMs at risk of OutOfMemoryError, or (7) replacing WRKJVMJOB command output.

IBM i Java & JVM Monitoring

Monitor Java Virtual Machines running on IBM i including heap memory, garbage collection, thread counts, and configuration using QSYS2.JVM_INFO.

Available Tools

The ibmi CLI is the primary tool for executing JVM queries. Set SKILL_DIR to this skill's installed location (the directory containing this SKILL.md file):

# SKILL_DIR = directory containing this SKILL.md
# Examples: ./skills/java, ~/.claude/skills/java

ibmi tools --tools "$SKILL_DIR/tools/" --toolset java_default
ibmi tool list_jvms --tools "$SKILL_DIR/tools/"
ibmi sql "SELECT JOB_NAME, CURRENT_HEAP_SIZE, IN_USE_HEAP_SIZE FROM QSYS2.JVM_INFO"

Service Selection Guide

JVM Monitoring

• QSYS2.JVM_INFO (VIEW) -- Quick overview of all active JVMs
• QSYS2.JVM_INFO (TABLE FUNCTION) -- Detailed JVM data with wait time parameter for memory breakdown (malloc, internal, JIT, shared class)

Key Capabilities

Memory Analysis

• Heap Usage -- Current, in-use, and maximum heap sizes per JVM
• Memory Breakdown -- Malloc, internal, JIT, and shared class memory (via table function)
• Threshold Alerts -- Find JVMs exceeding heap usage percentages

Performance Monitoring

• Garbage Collection -- Total GC time and cycle counts
• Thread Counts -- Java thread count per JVM
• Uptime -- JVM start times for stability tracking

Configuration

• Java Home -- Which Java version each JVM uses
• User Directory -- Working directory for each JVM
• Properties -- Number of configured properties per JVM
• Bit Mode -- 32-bit vs 64-bit JVM identification

Common Use Cases

1. Find memory-hungry JVMs -- Sort by heap usage to identify top consumers
2. Detect GC pressure -- High GC time or cycle count indicates memory issues
3. Capacity planning -- Track heap growth trends across JVMs
4. Java version audit -- Identify which Java homes are in use
5. Troubleshoot OutOfMemoryError -- Find JVMs near max heap

Quick Examples

List all active JVMs

ibmi tool list_jvms --tools "$SKILL_DIR/tools/"

Find JVMs using more than 80% heap

ibmi tool list_jvms_by_heap_usage --tools "$SKILL_DIR/tools/" --min-heap-pct 80

Get detailed memory breakdown

ibmi tool get_jvm_detail --tools "$SKILL_DIR/tools/" --wait-time 10

Find JVMs with high GC activity

ibmi tool list_jvms_by_gc_activity --tools "$SKILL_DIR/tools/" --min-gc-cycles 100

Pre-built Tools

The tools/java.yaml file provides 5 ready-to-use tools:

Tool	Description
list_jvms	List all active JVMs with memory and GC stats
get_jvm_detail	Detailed JVM info including memory breakdown
list_jvms_by_heap_usage	Find JVMs by heap consumption percentage
list_jvms_by_gc_activity	Find JVMs with highest GC activity
get_jvm_properties	JVM configuration and property counts

ibmi tool <tool_name> --tools "$SKILL_DIR/tools/"          # Execute
ibmi tool <tool_name> --tools "$SKILL_DIR/tools/" --dry-run # Preview SQL
ibmi tools show <tool_name> --tools "$SKILL_DIR/tools/"     # View details

Reference Documentation

• Java Services Catalog -- Available SQL services
• Example SQL Patterns -- Working query examples
• IBM JVM_INFO -- View documentation