Question & Answer
Question
IBM Java for AIX HowTo: Resolve core dumps by processes running on Power 8
Answer
If all of these steps have been completed and the problem persists, then it is recommended that you open a new IBM support call with the IBM AIX Java Support team for a more in-depth analysis into the issue. Prior to any additional analysis, the IBM AIX Java Support team will confirm that all of these steps have been completed since this is a well known and documented issue.
Generic Term | Replace with |
PMR | The full IBM PMR number (e.g. , PMR12345.b678.c000). |
Applications using IBM Java for AIX using Power 8 hardware with Power 8 mode enabled, may generate process core dumps due to a known issue with Event-Based Branching facility (EBB) and the enhanced Performance Monitoring Unit (PMU).
IBM Java version 8.0 for AIX, uses the Power 8 Runtime Instrumenation (RI) feature facilitated by EBB facility and the PMU and therefore, Java 8 is susceptible to experiencing these application crashes. The most commonly reported scenarios are:
- When attempting to use Live Partition Mobility (LPM) with running Java processes
- When executing tprof (as a command or through a performance data collection script) in parallel to running Java processes
The active Java processes will terminate and generate process core dumps during these common scenarios.
More advanced users with ability to analyze the dumps, can check for references to "MMCR0" register as cause of the issue from the core files.
Recommendations are listed below to resolve this issue.
Below is a list of workarounds that may resolve the issue as an alternative to applying an ifix:
AIX Workarounds:
1) Run in Power 7 Compatibility Mode as a temporary fix.
2) If migrating using LPM, stop the processes before the migration and restart them after the migration, to avoid processes from crashing.
Option 1:
Upgrade IBM Java 8.0 to SR5 or above to prevent the core dumps issue.
To upgrade stand alone IBM Java 8, please follow instructions as per:
http://www-01.ibm.com/support/docview.wss?uid=isg3T1022693
If you need assistance with upgrading WebSphere packaged Java, please open a new IBM support call with the IBM WebSphere Support team.
If the existing IBM Java 8.0 installs cannot be upgraded immediately, please make sure IBM Java 8.0 applications, are restarted after applying one of the options listed below to avoid crashes.
There are no expected side effects or impact to Java applications or agents after the upgrade. This option requires a restart of the process.
Option 2:
-XX:-RuntimeInstrumentation
No side effects or impact is expected for the Java applications or agents after applying the command line option. This option requires a restart of the process.
Option 3:
The issue can be avoided by running the system in Power 7 Compatibility Mode.
To determine the processor mode, at the command prompt, execute the following command:
# prtconf | grep "Processor Implementation Mode"
CPU Compatibility Mopde can be changed to POWER 7 from the HMC through the LPAR properties, following the steps below:
i. Select the LPAR and deactivate it.
ii. Go to Configuration -> Manage Profiles.
iii. Select the profile that needs to be activated.
iv. Go to Processors, change the Processor compatibility mode to Power 7 and boot it using the same profile.
This option requires a restart of the system.
Option 4:
If migrating using LPM, stop the processes before the migration and restart them after the migration, to avoid processes from crashing.
For example, from a command line prompt, run the following commands to identify the Java applications using Java 7.1 or Java 8:
# ps -ef | grep java
For each command listed, work with the appropriate system's or application's administrator to temporarily shutdown these processes using IBM Java 8.0, before using LPM and restart once LPM has completed.
Below is a list of workarounds that may resolve the issue as an alternative to applying a fix:
AIX Workarounds:
IV97097: JAVA 1.8 PROCESS COREDUMP DUE TO EBB ILL INST WHEN TPROF IS RUN (AIX 7200-02)
IV96941: JAVA 1.8 PROCESS COREDUMP DUE TO EBB ILL INST WHEN TPROF IS RUN (AIX 7200-01)
IV97096: JAVA 1.8 PROCESS COREDUMP DUE TO EBB ILL INST WHEN TPROF IS RUN (AIX 7200-00)
IV96353: JAVA 1.8 PROCESS COREDUMP DUE TO EBB ILL INST WHEN TPROF IS RUN (AIX 7100-04)
IV97095: JAVA 1.8 PROCESS COREDUMP DUE TO EBB ILL INST WHEN TPROF IS RUN (AIX 7100-05)
If, after following the above instructions, the application continues to generate core dumps, please complete the following steps:
1. Confirm that you have completed all of the above steps.
2. Contact IBM and open a new IBM service request (new PMR).
3. Collect and upload data as per the data collection procedure for automatically generated process core dumps.
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Document Type: | Instruction |
Content Type: | Howto |
Hardware: | Power 8 |
Operating System: | AIX 7.1 and 7.2 |
IBM Java: | Java 8.0 |
Author(s): | Vidya Makineedi |
Reviewer(s): | Roger Leuckie |
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Document Information
Modified date:
17 June 2018
UID
isg3T1024484