WebSphere Enterprise Service Bus for z/OS, Version 6.2.0 Operating Systems: z/OS


Peer recovery

Peer recovery is recovery as performed by another member of the same cluster, and can be initiated either manually or automatically. Peer recovery processing (either automated peer recovery or manual peer recovery) is tightly intertwined with the WebSphere's high availability environment.

High availability manager

WebSphere® employs a High Availability Manager component to monitor services provided by the application server. These services include messaging, transaction managers, workload management controllers and other application servers in a cluster. The High Availability Manager component also makes use of Network-attached storage (NAS) devices to store transaction logs from each application server in the cluster.

The High Availability Manager is responsible for the automatic peer recovery of both indoubt and inflight transactions for any server that fails in the defined HA cluster. An indoubt transaction is any transaction that becomes stuck in the indoubt state indefinitely, because of an exceptional circumstance such as the removal of a node causing messaging engines to be destroyed. An indoubt transaction state results after the database finishes its phase 1 commit processing and before it starts phase 2. An inflight transaction is a transaction that has not yet completed the "prepare phase" of the commit process and where the transaction or message is persisted somewhere where it can be recovered. The automatic recovery functionality performed by the High Availability Manager enables the cluster to rebalance itself if one or more cluster members fail.

Automated peer recovery vs. manual peer recovery

Automated peer recovery is the default style of peer recovery initiation. If an application server fails, WebSphere Application Server automatically selects a server to perform peer recovery processing on its behalf. Apart from enabling high availability and configuring the recovery log location for each cluster member, no additional WebSphere Application Server configuration steps are required to use this model.

Manual peer recovery is a particular style of peer recovery that must be explicitly configured. If an application server fails, the operator can use the administrative console to select a server to perform recovery processing on its behalf.

Peer recovery reference information

The article titled IBM® WebSphere Developer Technical Journal: Transactional high availability and deployment considerations in WebSphere Application Server V6 discusses the requirements, setup, and management of both automated and manual peer recovery.

Additional documentation can be found in the WebSphere Application Server information center and in the WebSphere Application Server V6 Scalability and Performance Handbook.

reference Reference topic

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Timestamp icon Last updated: 21 June 2010


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