user manual

Chapter 19: Transaction management 195
Chapter
19
Chapter19Transaction management
This chapter describes how to handle transactions.
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Understanding transactions
Application programmers benefit from developing their applications on
platforms such as Java 2 Enterprise Edition (J2EE) that support transactions.
A transaction-based system simplifies application development because it
frees the developer from the complex issues of failure recovery and multi-user
programming. Transactions are not limited to single databases or single sites.
Distributed transactions can simultaneously update multiple databases across
multiple sites.
A programmer typically divides the total work of an application into a series of
units. Each unit of work is a separate transaction. As the application
progresses, the underlying system ensures that each unit of work, each
transaction, fully completes without interference from other processes. If not, it
rolls back the transaction and completely undoes whatever work the
transaction had performed.
Characteristics of transactions
Typically, transactions refer to operations that access a shared resource like a
database. All access to a database is performed in the context of a
transaction. All transactions share the following characteristics: