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Nodeagent restarts all application servers on the node when DNS server is down

Troubleshooting


Problem

Nodeagent restarts all application servers on the node when DNS server is down if the system is not configured to use IPv6 in /etc/hosts. This problem occurs on IBM WebSphere Application Server V5.1 and V6.0 (all releases) and does not occur on V5.0.

Cause

In Java™ 2 SDK 1.4, JVM performs both IPv6 and IPv4 queries. If the system is not configured to use IPv6 in /etc/hosts, IPv6 queries will fail when DNS server is down. Nodeagent checks the status of applications on the node at one minute interval by way of the network. If nodeagent can not connect to an application server, it will assume that the server is hung and try to restart the server. So if nodeagent fails to lookup the hostname of its node, it will restart all the application servers in the same node.

Resolving The Problem

To solve this problem, you can select either way from the following 2 options;

  • Java solution
    Set the JVM custom property java.net.preferIPv4Stack to all servers including nodeagent and dmgr.
    1. Open the administrative console and navigate to:

      System Administration > Application Servers > server_name > Process Definition > Java Virtual Machine > Custom Properties

    2. Add the following name and value pair:

      Name: java.net.preferIPv4Stack
      Value: true

    3. Click Apply, then save all changes.

    4. Restart the application server.

  • AIX solution
    The following AIX APARs address this issue:

    For AIX V520: IY47908
    For AIX V510: IY48783

    Ensure that you AIX V5.1 and V5.2 systems are at the latest maintenance level.

    Run the following:

    vi /etc/netsvc.conf
    hosts=local,bind4

    or

    export NSORDER=local,bind4

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Document Information

Modified date:
15 June 2018

UID

swg21251377

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