Transaction Modes in Teredata Teradata

The Teradata database software was originally written to be compatible with DB/2, the IBM mainframe RDBMS (Relational Data Base Management System). It was developed primarily as a database computer to be connected to mainframe systems. In the years since then, Teradata has evolved to include connections to network attached computers.

Another evolution for Teradata is the inclusion of ANSI (American National Standards Institute) standards in its functionality and the format of its SQL commands. This allows users to learn SQL commands once and use them on several RDBMS systems. At the same time, most RDBMS vendors provide extensions to their database that extend the functionality of their SQL. These extensions are what vendors call "value add." Extensions may take advantage of a particular strength of the RDBMS or provide a unique functionality to make the user's life easier.

It is good that all of the RDBMS vendors are conforming to the standards. This way the same request on different systems does not create unexpected results on various systems. Teradata is a mature RDBMS and existed before the standards were defined. Therefore, some of the techniques and commands for Teradata became part of the standard; others did not. When the standard operation contradicts what customers have come to count on, there exists the opportunity for confusion.

To resolve this potential problem, Teradata allows a user to specify which transaction mode to use for any SQL statement. The normal system default for a Teradata system is Teradata mode. However, Teradata can be configured to use ANSI mode as the system default. To establish a site-specific system default, the system administrator can change the DBS Control Record as an administrative function.

Regardless of which mode is set as the system default, a user can over-ride it for a session. This means that a system running in Teradata mode can use ANSI mode for one or more SQL statements and of course, the opposite is also true. As far as the SQL is concerned, the syntax does not change. Whether in Teradata or ANSI mode, the SQL is always written exactly the same. ANSI commands work in Teradata mode and Teradata extensions work in ANSI mode. THE SQL DOES NOT NEED TO CHANGE to match the mode. However, the output data may vary from one mode to the other based on the conditions outlined in the chart on the following page.

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