1.3.4 Transaction Recovery

The atomicity property of a transaction guarantees that all participants in the transaction receive the same outcome. This guarantee is relaxed in the case of volatile resources such as voters but is strictly honored for durable resource managers and transaction managers.

To honor this guarantee, transaction managers and durable resource managers have to be capable of recovering from transient failures that can occur, such as loss of transport connectivity or a software crash. The process of recovery involves reestablishing connectivity with other transaction participants and exchanging the protocol messages that are required to synchronize all parties on the actual outcome of the transaction.

After a transient failure, the transaction manager reestablishes connectivity with the following parties:

• The superior transaction manager for each transaction for which the transaction manager was In Doubt at the time of the failure

• The subordinate transaction managers for which the transaction manager was in the Failed to Notify state at the time of the failure

After a transient failure, the resource manager reestablishes connectivity with the following parties:

• The superior transaction manager for each transaction for which the resource manager was In Doubt at the time of the failure

The following sections describe in more detail the recovery process for each participant.