Compaq AA-Q88CE-TE manual Transaction Management

4

Transaction Management

4.1 Overview

This section describes the concepts of RTR's transaction management capability.

The RTR transaction is the heart of an RTR application, and transaction state is the property that characterizes a transaction's current condition. Whenever a transaction progresses from one stage to another, the transaction state is updated to reflect a transaction transition. Transaction states are maintained in memory and some types of transaction states are also stored in the RTR Journal for recovery purposes.

Three different types of states are used internally by RTR to keep track of transaction status.

•Transaction Runtime State

•Transaction Journal State

•Transaction Server State

These three state types are very closely related. The Transaction Runtime State, also known as Transaction State, describes how a transaction progresses from a RTR role (FE, TR, BE) point of view. For example, a transaction can enter a stage in which its transaction state from an RTR frontend viewpoint is different than the transaction state of an RTR router.

The Transaction Journal State describes how a transaction running on an RTR backend progresses from the RTR journal perspective. When a transaction transitions, its Transaction Journal State gets updated and the new state along with other information pertaining to this transaction is stored in the RTR journal. The Transaction Journal State is primarily used by RTR to perform the recovery replay of a transaction after a failure, if necessary. An RTR frontend and router will not see this state.

The Transaction Server State describes transaction state transition seen by the server. RTR uses this state to determine if a server is available to process a new transaction or if a server has voted on a particular transaction. As with the Transaction Journal State, the Transaction Server State is only managed at the backend.

RTR provides a set of comprehensive management utilities to help users closely monitor the flow of a transaction and all three types of states associated with that transaction. These utilities help users understand how a transaction migrates from one stage to another and help diagnose problems.

The RTR SHOW TRANSACTION command can be used to examine a transaction's up-to-date status on frontend, router or backend roles. With this command, users can see all three types of transaction states of a particular transaction and also understand how the RTR journal and application servers perceive this transaction. When a transaction commits or aborts, all status associated with

Transaction Management 4–1