Introduction: Transactions

Explore the key concepts pertaining to applications that conduct transactions. Applications running on the server can use transactions to coordinate multiple updates to resources as one unit of work such that all or none of the updates are made permanent. The product provides advanced transactional capabilities to help application developers avoid custom coding. It provides support for the many challenges related to integrating existing software assets with a J2EE environment. These measures include ActivitySessions (described elsewhere).

Transaction support in WebSphere Application Server

A transaction is unit of activity within which multiple updates to resources can be made atomic (as an indivisible unit of work) such that all or none of the updates are made permanent. For example, multiple SQL statements to a relational database are committed atomically by the database during the processing of an SQL COMMIT statement. In this case, the transaction is contained entirely within the database manager and can be thought of as a resource manager local transaction (RMLT). In some contexts, a transaction is referred to as a logical unit of work (LUW). If a transaction involves multiple resource managers, for example multiple database managers, then an external transaction manager is required to coordinate the individual resource managers. A transaction that spans multiple resource managers are referred to as a global transaction. WebSphere Application Server is a transaction manager that can coordinate global transactions, be a participant in a received global transaction and also provides an environment in which resource manager local transactions can run.

Approaches to coordinating access to one-phase commit and two-phase commit capable resources within the same transaction

Last participant support enables the use of a single one-phase commit capable resource with any number of two-phase commit capable resources in the same global transaction. You can have multiple interactions that involve the one-phase commit resource in the same transaction, but only one such resource can be involved.

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