| Previous | Table of Contents | Next |
The standard for Fault Tolerant CORBA aims to provide robust support for applications that require a high level of reliability,
including applications that require more reliability than can be provided by a single backup server. The standard requires
that there shall be no single point of failure.
Fault tolerance depends on entity redundancy, fault detection, and recovery. The entity redundancy by which this specification
provides fault tolerance is the replication of objects. This strategy allows greater flexibility in configuration management
of the number of replicas, and of their assignment to different hosts, compared to server replication. Replicated objects
can invoke the methods of other replicated objects without regard to the physical location of those objects. Support for redundancy
in time is provided by allowing clients to make repeated requests on the server, using the same or alternative transport paths.
The standard supports a range of fault tolerance strategies, including request retry, redirection to an alternative server,
passive (primary/backup) replication, and active replication which provides more rapid recovery from faults. The standard
allows the users to define fault tolerance properties for each replicated object (object group).
The standard supports applications that require the Fault Tolerance Infrastructure to control the creation of the application
object replicas, as well as applications that control directly the creation of their own object replicas. It supports applications
that require the Fault Tolerance Infrastructure to maintain Strong Replica Consistency, both under normal conditions and under
fault conditions, as well as applications that provide whatever level of consistency they require.
The standard provides support for fault detection, notification, and analysis for the object replicas. It supports applications
that require the Fault Tolerance Infrastructure to provide automatic checkpointing, logging and recovery from faults, as well
as applications that handle their own fault recovery.
The standard aims for minimal modifications to the application programs, and for transparency to replication and to faults.
It defines minimal modifications to existing ORBs that allow non-replicated clients to derive fault tolerance benefits when
they invoke replicated server objects.