org.omg.CosTransactions

Interface ResourceOperations

public interface ResourceOperations

The Transaction Service uses a two-phase commitment protocol to complete a top-level transaction with each registered resource. The Resource interface defines the operations invoked by the transaction service on each resource. Each object supporting the Resource interface is implicitly associated with a single top-level transaction. Note that in the case of failure, the completion sequence will continue after the failure is repaired. A resource should be prepared to receive duplicate requests for the commit or rollback operation and to respond consistently.
Method Summary
voidcommit()
If necessary, the resource should commit all changes made as part of the transaction.
voidcommit_one_phase()
If possible, the resource should commit all changes made as part of the transaction.
voidforget()
This operation is performed only if the resource raised a heuristic outcome exception to rollback, commit, or commit_one_phase.
Voteprepare()
This operation is invoked to begin the two-phase commit protocol on the resource.
voidrollback()
If necessary, the resource should rollback all changes made as part of the transaction.

Method Detail

commit

public void commit()
If necessary, the resource should commit all changes made as part of the transaction. If the resource has forgotten the transaction, it should do nothing. The heuristic outcome exceptions are used to report heuristic decisions related to the resource. If a heuristic outcome exception is raised, the resource must remember this outcome until the forget operation is performed so that it can return the same outcome in case commit is performed again. Otherwise, the resource can immediately forget all knowledge of the transaction. The NotPrepared exception is raised if the commit operation is performed without first performing the prepare operation.

commit_one_phase

public void commit_one_phase()
If possible, the resource should commit all changes made as part of the transaction. If it cannot, it should raise the TRANSACTION_ROLLEDBACK standard exception. If a failure occurs during commit_one_phase, it must be retried when the failure is repaired. Since their can only be a single resource, the HeuristicHazard exception is used to report heuristic decisions related to that resource. If a heuristic exception is raised, the resource must remember this outcome until the forget operation is performed so that it can return the same outcome in case commit_one_phase is performed again. Otherwise, the resource can immediately forget all knowledge of the transaction.

forget

public void forget()
This operation is performed only if the resource raised a heuristic outcome exception to rollback, commit, or commit_one_phase. Once the coordinator has determined that the heuristic situation has been addressed, it should issue forget on the resource. The resource can forget all knowledge of the transaction.

prepare

public Vote prepare()
This operation is invoked to begin the two-phase commit protocol on the resource. The resource can respond in several ways, represented by the Vote result. If no persistent data associated with the resource has been modified by the transaction, the resource can return VoteReadOnly. After receiving this response, the Transaction Service is not required to perform any additional operations on this resource. Furthermore, the resource can forget all knowledge of the transaction. If the resource is able to write (or has already written) all the data needed to commit the transaction to stable storage, as well as an indication that it has prepared the transaction, it can return VoteCommit. After receiving this response, the Transaction Service is required to eventually perform either the commit or the rollback operation on this object. To support recovery, the resource should store the RecoveryCoordinator object reference in stable storage. The resource can return VoteRollback under any circumstances, including not having any knowledge about the transaction (which might happen after a crash). If this response is returned, the transaction must be rolled back. Furthermore, the Transaction Service is not required to perform any additional operations on this resource. After returning this response, the resource can forget all knowledge of the transaction. The resource reports inconsistent outcomes using the HeuristicMixed and HeuristicHazard exceptions. Heuristic outcomes occur when a resource acts as a sub-coordinator and at least one of its resources takes a heuristic decision after a VoteCommit return.

rollback

public void rollback()
If necessary, the resource should rollback all changes made as part of the transaction. If the resource has forgotten the transaction, it should do nothing. The heuristic outcome exceptions are used to report heuristic decisions related to the resource. If a heuristic outcome exception is raised, the resource must remember this outcome until the forget operation is performed so that it can return the same outcome in case rollback is performed again. Otherwise, the resource can immediately forget all knowledge of the transaction.