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C H A P T E R 8 Transactions and Versioning

About this chapter	This chapter describes Adaptive Server IQ’s approach to transaction
	processing, called snapshot versioning, and its implications for
	performance and other aspects of database administration.

Overview of transactions and versioning

Adaptive Server IQ uses transaction processing to allow many users to read from the database while it is being updated. Transaction processing ensures that logically related commands are executed as a unit. Transactions are fundamental to maintaining the accuracy of your data, and to data recovery in the event of system failure.

A crucial aspect of transaction processing is its ability to isolate users from the effect of other users’ transactions. Adaptive Server IQ’s approach to transaction processing, called snapshot versioning, supports the highest level of isolation recognized by ISO.

Introduction to transactions

Transactions are simply groups of SQL statements. Each transaction performs a task that changes your database from one consistent state to another. These units play an important role in protecting your database from media and system failures, and in maintaining the consistency of your data.

Transactions are logical units of work

A transaction is a logical unit of work. Each transaction is a sequence of logically related commands that accomplish one task and transform the database from one consistent state into another.

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