![]() ![]() ![]() Managed Servers maintain a local copy of the domain configuration. This capability improves the availability of pinned services in a cluster, because those services can be quickly restarted on a redundant server should the host server fail. Singleton services are services that run in a cluster but must run on only a single instance at any given time, such as JMS and the JTA transaction recovery system.Īn administrator can migrate a JMS server or the JTS transaction recovery from one server instance to another in a cluster, either in response to a server failure or as part of regularly-scheduled maintenance. WebLogic Server supports migration of a individual singleton service as well as the server-level migration capability described in the previous section. For more information, see Server Migration in Using WebLogic Server Clusters. The migration process makes all of the services running on the server instance available on a different machine, but not the state information for the singleton services that were running at the time of failure. A clustered server that is configured to be migratable can be moved in its entirety from one machine to another, at the command of an administrator, or automatically, in the event of failure. WebLogic Server 9.0 provides the capability to migrate clustered server instances. This improves the overall reliability of a domain, and requires no direct intervention from an administrator.įor more information, see Using Node Manager to Control Servers. Using Node Manager, server self-health monitoring enables you to automatically reboot servers that have failed. If one or more of its critical subsystems have reached the FAILED state, the server instance marks its own health state FAILED to indicate that it cannot reliably host an application. If an individual subsystem determines that it can no longer operate in a consistent and reliable manner, it registers its health state as "failed" with the host server.Įach WebLogic Server instance, in turn, checks the health state of its registered subsystems to determine its overall viability. For example, the JMS subsystem monitors the condition of the JMS thread pool while the core server subsystem monitors default and user-defined execute queue statistics. Selected subsystems within each WebLogic Server instance monitor their health status based on criteria specific to the subsystem. WebLogic Server self-health monitoring improves the reliability and availability of server instances in a domain. Auto matic Restart for Failed Server Instances Clusterable services, such as EJBs and Web applications, can be deployed uniformly-on each Managed Server-in a cluster, so that if the server instance upon which a service is deployed fails, the service can fail over to another server in the cluster, without interruption in service or loss of state.įor more information, see Failover and Replication in a Cluster in Using WebLogic Server Clusters. You can increase the reliability and availability of your applications by hosting them on a WebLogic Server cluster. HTTP session count increases to a predefined threshold value.WebLogic Server attempts to avoid failure when certain conditions occur: Overload protection helps you avoid failures that result from unanticipated levels of application traffic or resource utilization. WebLogic Server 9.0 detects increases in system load that can affect application performance and stability, and allows administrators to configure failure prevention actions that occur automatically at predefined load thresholds. WebLogic Server offers several features that facilitate recovery from and protection against server failure. Restarting a Failed Administration Server.WebLogic Server Exit Codes and Restarting After Failure.Directory and File Backups for Failure Recovery.Failure Prevention and Recovery Features.The following sections provide information and procedures for recovering failed server instances: (For information about failover in a WebLogic Server cluster, see Failover and Replication in a Cluster in Using WebLogic Server Clusters.) However, even in a clustered environment, server instances may fail periodically, and it is important to be prepared for the recovery process. Loss of power, hardware malfunction, operating system crashes, network partitions, and unexpected application behavior can all contribute to the failure of a server instance.įor high availability requirements, implement a clustered architecture to minimize the impact of failure events. Often one failure condition leads to another. Avoiding and Recovering From Server FailureĪ variety of events can lead to the failure of a server instance. ![]()
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