High availability environment troubleshooting tips

 

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Review the following topics if you encounter a problem with your high availability environment.

 

Message HMGR0218I is not displayed after a Java Virtual Machine starts

In a properly set up high availability environment, a high availability manager can reassess the environment it is managing and accept new components as they are added to the environment. For example, when a JVM is added to the infrastructure, a discovery process begins. During startup the JVM tries to contact the other members of the core group. When it finds another running JVM, it initiates a join process with that JVM that determines whether or not the JVM can join the core group. If the new JVM is accepted as a member of the core group, all of the JVMs, including the new one, log message HMGR0218I . This message is also displayed on the console.

Message HMGR0218I indicates the number of appservers in the core group that are currently online. If this message is not displayed after a JVM starts, either a configuration problem or a communication problem has occurred. To fix this situation, verify that the appserver is running on a current configuration, by either using the deployment manager to tell the node agent to synchronize, or use the syncNode command o manually perform the synchronization. If the JVM still cannot join the core group, a network configuration problem exists.

 

Message HMGR0123I appears in the system log file

Message HMGR0123I might appear in the system log file if the status of core group members changes at the same time as the active coordinator changes. For example, this message might be issued when a core group member restarts and becomes the active coordinator.

This information message usually does not indicate a serious problem. Even if this message appears in the system log file, the new active coordinator receives the updated group status. If you want to minimize the occurrences of this message, you should select a core group member that does not frequently restart as the preferred core group coordinator.

 

CPU starvation messages in the system log file

CPU starvation detected error messages are displayed in the system log file whenever there is not enough physical memory available to allow the high availability manager threads to have consistent runtimes. When the CPU is spending the majority of its time trying to load swapped-out processes while processing incoming work, thread starvation might occur. The high availability manager detects this condition, and logs these error messages informing you that threads are not getting the required runtime.

To achieve good performance and avoid receiving these error messages, it is recommended that you allocate at least 512 MB of RAM for each Java process running on a single machine.

 

High CPU usage in a large cell configuration when security is enabled

With certain configurations and states, the amount of time spent in discovery becomes substantial.

To decrease the CPU time spent in discovery:

  1. In the console, click Servers > Core groups > Core groups settings , and then select the -> DefaultCoreGroup.

  2. Under Additional Properties, click Custom properties > New.

  3. Enter IBM_CS_UNICAST_DISCOVERY_INTERVAL_SECS in the Name field and 120 in the Value field.

  4. Click OK.

  5. Then click New again and enter IBM_CS_SS_SECURE_TOKEN in the Name field andfalse in the Value field.

  6. Click OK and then Save to apply these changes to the master configuration.

  7. Restart the server for these changes to take effect.




 

Related concepts

Core group coordinator

 

Related tasks

Configure core group preferred coordinators
Setting up a high availability environment

 

Related Reference

syncNode command