Oracle Database 11 g - Online Public Access Catalog

CHAPTER 1 ■ INSTALLING, UPGRADING, AND MANAGING CHANGE 35Real Application TestingAdopting new technologies is too often a double-edged sword, making you more efficient andthus providing a competitive advantage while simultaneously introducing uncertainty andpotential instability into key production systems. Change assurance, which involves makingsure major changes such as new software releases and database upgrades don’t negativelyimpact performance, has always been a prime concern for Oracle application developers anddatabase administrators. Even if you can simulate real production workloads, the effort is justthat—a simulation, not the real deal. In a world that is technologically advancing at a mindnumbingpace, you need to know which of the technologies have the potential to benefit you;therefore, you need to perform real testing with real data in real conditions.Oracle Database 11g places considerable emphasis on the proactive testing of changes bymaking change assurance one of the cornerstones of the new release. It does this through theReal Application Testing feature; this feature encompasses two components, Database Replayand the SQL Performance Analyzer, that dramatically reduce the risks inherent in adoptingchanges by offering you a realistic method of testing changes using real-life workloads. Thetools unearth problems and give you the opportunity to fix them before you actually introducethe changes into your production systems. Here’s a brief summary of the two key componentsof Real Application Testing in Oracle Database 11g:• Database Replay: You can use the Database Replay feature to test the impact of the databaseupgrade on the production workload by capturing and replaying the productionworkload on a test system before you actually perform the upgrade on your productiondatabase. Using the Database Replay reports from a test server, you can fix potentialproblems before they occur on the production database. We discuss the Database Replayfeature later in this chapter.• SQL Performance Analyzer (SPA): You can use the SQL Performance Analyzer to predictthe impact of any change, such as an upgrade to a new release, on the SQL workload ascaptured by a SQL tuning set. By knowing ahead of the actual upgrade about any adverseimpact on performance and the root cause for it, you can prevent it from actually occurringin a production database after a database upgrade. We discuss the SPA later in this chapter.In addition to the Database Replay and the SQL Performance Analyzer features, there’salso a third new feature pertaining to change management, called SQL Plan Management,which replaces the stored outlines feature in earlier releases. The SQL Plan Managementfeature relies on the use of SQL plan baselines, which represent efficient execution plans.When you adopt SQL Plan Management pursuant to a database upgrade, only those SQL plansare used that don’t result in a performance regression. We discuss the SPA in detail in Chapter 3.Wediscuss Database Replay and the SQL Performance Analyzer in detail in the following sections.Database ReplayOne of the major problems you face during an Oracle server software upgrade process or anapplication upgrade is the difficulty in simulating the actual production workload on the testdatabases. This is also true when you’re moving to a totally new database configuration, sayfrom a regular operating system file system to automatic storage management. Even if you usesophisticated testing suite software, it’s not easy to accurately reproduce the true workload of