Oracle Database 11 g - Online Public Access Catalog

36 CHAPTER 1 ■ INSTALLING, UPGRADING, AND MANAGING CHANGEa production database. Consequently, you are forced to test in an unrealistic setting and takeyour chances when you move to the new release of the server software or the application. It’snot at all uncommon for DBAs and developers to bemoan the fact that the testing folks couldn’tadequately “stress test” the changes before they were approved for the switch to production.■Note You can capture the workload for a single-instance Oracle database and replay it over a test systemrunning in Oracle RAC configuration to get an idea about the performance improvement.The Database Replay feature provides a solution to the vexing problem of reproducingproduction conditions in the testing and migration environments. By making it significantlyeasier to test potential database changes, Oracle Database 11g lowers the cost of databaseupgrades as well as other major changes such as operating system and storage system upgrades.Testing that usually would take months when done by scripts and traditional load simulationtools can be done at dazzlingly fast speeds now with the Database Replay feature. DatabaseReplay lets you capture the actual workload on a production system and analyze it the sameway by replaying it on a test system. The goal is to replicate the production environment in totoon a test system. Since the characteristics of the original workload such as concurrency andtiming are maintained during the replay, you’re essentially working with the same type of resourcecontention and other characteristics. This lets you easily identify any negatives that’ll be potentiallyintroduced by making the application, system, or software changes. The goal is to make surethe change you’re making, such as a database upgrade, gets you only desirable results. Notethat your test system must be running on the same or a newer version of the Oracle Databasecompared to the production system.The key fact you must understand here is that Database Replay captures only the workloadat the database level and ignores all client, application, and middle-tier interactions. The replay willcapture the impact of any system changes that affect the database, such as an upgrade of thedatabase itself, an upgrade of the operating system, or a switch to a new disk storage system.The production database is backed up and restored on a test system with identical configurationand environment. Your goal is to replicate the production system with the same application stateas the original.You can use Database Replay for testing the following types of changes:• Database upgrades• Operating system upgrades• Storage system changes• Configuration changes such as switching to an Oracle Real Application ClusterUsing Database Replay to replay a production workload consists of four steps:1. Workload Capture records the production database workload.2. Workload Preprocessing makes the captured workload replayable by converting it intoreplay files.