Overview
* Service migration is the process of moving the pinned services from one server instance to a different available server instance within the cluster.
* Service migration is performed on a logical migratable target:
– logical grouping of services
– hosted on only one physical server in a cluster.
* High availability is achieved by migrating a migratable target from one clustered server to another when a problem occurs on the original server.
* To clients, services configured to use a migratable target is independent from underlying hosting server instance.
* Can be automatic or manual process as defined by migration policies.
– manual policy (default)
– exactly-once policy: if at least one Managed Server in the candidate list is running, then the service will be active somewhere in the cluster if servers fail or are shut down (either gracefully or forcibly).
– failure-recovery policy: migrate if and only if the user-preferred server (UPS) fails due to an internal error and constrained candidate server (CCS) is specified.
* Admin server is not required when migrating services.
* Examples of pinned services:
– JMS related services
~ JMS Server
~ Store-and-Forward (SAF) Service
~ Path Service
~ Custom Persistent Store
– JTA Transaction Recovery Service
– User defined singleton services