Troubleshooting
Problem
During problem determination of Java application and IBM WebSphere heap-related problems, the Rochester Support Center often requests GC cycle dumps. This document provides the detailed instructions required to obtain these dumps. Actions below are relative to the Classic Java Development Kit
Resolving The Problem
To dump the last 500 GC cycles for a JVM, the JAVAGCINFO Advanced Analysis macro can be used. To gather the GC cycles history, refer to the following instructions.
The JAVAGCINFO Advanced Analysis macro requires that you know the fully qualified job of the JVM you want to analyze. Use the WRKACTJOB command to find the job information, and write it down before you continue with the following steps:
| 1. | On the operating system command line, type the following: STRSST Press the Enter key. |
| 2. | Type a user ID and password, and press the Enter key. |
| 3. | Select Option 1, Start a service tool, and press the Enter key. |
| 4. | Select Option 4, Display/Alter/Dump, and press the Enter key. |
| 5. | Select Option 1, Display/Alter storage, and press the Enter key. |
| 6. | Select Option 2, Licensed Internal Code (LIC) data, and press the Enter key. |
| 7. | Select Option 14, Advanced analysis, and press the Enter key. |
| 8. | Find JAVAGCINFO in the list of macros, and type 1 to select it (or select JAVAGCTOOLS for V5R2M0). After pressing the Enter key, the following is shown: Type options, press Enter. Command . . . . : JAVAGCINFO Options . . . . . |
| 9. | Press the Enter key with no options selected. By default it is -dumpjvms. This will provide summary information on all the JVMs currently active. A screen similar to the following should be shown: JVM General Information: VM*=CCBB587D1A06D780 Task=B00170000D903000 Task Name=MITHREAD-IWA61 QEJBSVR 362183 GC Object*=DDEA43D75C001500 Java New*=FA72613DE0CA1680 Clear Color=7 Ma Global Registry Entries=C57828A9A7001000 JNI Registry Entries=F65C5F05110 Number of GC Helper Threads: Total = 32 Node 0 = 32 Node 1 = 0 Node 2 = de 7 = 0 JVM Heap size Information. Sizes are in bytes: Initial Heap Size=100663296 Threshold Per Node = 100663296 Nodes = 8 Initial Maximum Heap Size=*NoMax Current Maximum Heap Size=*NoMax GC Heap Manager*=D02AB4F29F004700 Size=302688768 JVM Heap*=D02AB4F29F0000 JVM Problem Mode Heap*=DF467E9735000048 Size=15323136 JIT Heap=D5B02CF481 Garbage Collection Cycle Information. Duration Times In Milliseconds: There will be information for every active JVM on the system. Therefore, scroll down to find the appropriate JVM. The qualified job information follows Task Name=MITHREAD- (shown previously). You can also scroll to the right (using F10) to see the entire job name and so on. Make note of the VM* address (highlighted in blue) to the left of this. What follows the "VM*=" must be copied for use on commands that follow. |
| 10. | Continue to press F3 until you to return to the Display/Alter/Dump Output device screen. |
| 11. | Select Option 2, Dump to printer, and press the Enter key. |
| 12. | Select Option 2, Licensed Internal Code (LIC) data, and press the Enter key. |
| 13. | Select Option 14, Advanced analysis, and press the Enter key. |
| 14. | Find JAVAGCINFO in the list of macros and type 1 to select it and press the Enter key. In the Options, type -gccycles <vmaddress>. In the example, it is: Options . . . . . -gccycles CCBB587D1A06D780 |
| 15. | Press the Enter key two times to dump to a printer. |
| 16. | Exit SST. |
| 17. | Type the WRKJOB command, and select Option 4 to find the spooled file with the GC cycles information. |
Historical Number
369743336
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Document Information
Modified date:
18 December 2019
UID
nas8N1015671