1 Introduction to Oracle Real Application Testing

1.1 Database Replay

Before system changes are made, such as hardware and software upgrades, extensive testing is usually performed in a test environment to validate the changes. However, despite the testing, the new system often experiences unexpected behavior when it enters production because the testing was not performed using a realistic workload. The inability to simulate a realistic workload during testing is one of the biggest challenges when validating system changes.

Database Replay enables realistic testing of system changes by essentially re-creating the production workload environment on a test system. Using Database Replay, you can capture a workload on the production system and replay it on a test system with the exact timing, concurrency, and transaction characteristics of the original workload. This enables you to fully assess the impact of the change, including undesired results, new contention points, or plan regressions. Extensive analysis and reporting is provided to help identify any potential problems, such as new errors encountered and performance divergence.

Database Replay performs workload capture of external client workload at the database level and has negligible performance overhead. Capturing the production workload eliminates the need to develop simulation workloads or scripts, resulting in significant cost reduction and time savings. By using Database Replay, realistic testing of complex applications that previously took months using load simulation tools can now be completed in days. This enables you to rapidly test changes and adopt new technologies with a higher degree of confidence and at lower risk.

You can use Database Replay to test any significant system changes, including:

• Database and operating system upgrades

• Configuration changes, such as conversion of a database from a single instance to an Oracle Real Application Clusters (Oracle RAC) environment

• Storage, network, and interconnect changes

• Operating system and hardware migrations

1.2 SQL Performance Analyzer

System changes—such as a upgrading a database or adding an index—may cause changes to execution plans of SQL statements, resulting in a significant impact on SQL performance. In some cases, the system changes may cause SQL statements to regress, resulting in performance degradation. In other cases, the system changes may improve SQL performance. Being able to accurately forecast the potential impact of system changes on SQL performance enables you to tune the system beforehand, in cases where the SQL statements regress, or to validate and measure the performance gain in cases where the performance of the SQL statements improves.

SQL Performance Analyzer automates the process of assessing the overall effect of a change on the full SQL workload by identifying performance divergence for each SQL statement. A report that shows the net impact on the workload performance due to the change is provided. For regressed SQL statements, SQL Performance Analyzer also provides appropriate executions plan details along with tuning recommendations. As a result, you can remedy any negative outcome before the end users are affected. Furthermore, you can validate—with significant time and cost savings—that the system change to the production environment will result in net improvement.

You can use the SQL Performance Analyzer to analyze the impact on SQL performance of any type of system changes, including:

• Database upgrade

• Configuration changes to the operating system or hardware

• Schema changes

• Changes to database initialization parameters

• Refreshing optimizer statistics

• SQL tuning actions