The Three-Tier System Landscape 

With the three-tier system landscape, you make all of the changes to your system (to include Customizing) in a separate development system. You export these changes to a common transport directory. You then import these changes into a quality assurance system where you can thoroughly test them. Once you are satisfied that the changes are safe, you can then import them from the common transport directory into your productive system.

By following this recommendation, you provide for the following security measures:

·        You make sure that changes take place in only one location, namely the development system.

·        Your developers do not have access to productive data.

If you want to test with productive data, copy the subset of data that you want to use in the tests into the quality assurance system, and perform your tests there.

·        You can thoroughly test changes in a separate quality assurance system before they take effect in your productive system.

·        You control the point in time when changes take effect in the productive system.

·        You can reduce accidental or unauthorized changes to productive data by controlling when, from whom, and from which systems transfers take place.

·        You can keep a record of changes for tracing or auditing purposes.

If you discover errors in the quality assurance system that result in the need to make further changes, we recommend that you make the changes in the development system and re-import them into the quality assurance system.