This paper presents Oracle Database Replay, a novel approach to testing changes to the relational database management system component of an information system (software upgrades, hardware changes etc). Database Replay makes it possible to subject a test system to a real production system workload, which helps identify all potential problems before implementing the planned changes on the production system. Any interesting workload period of a production database system can be captured with minimal overhead. The captured workload can be used to drive a test system while maintaining the concurrency and load characteristics of the real production workload. Therefore, the test results using database replay can provide very high assurance in determining the impact of changes to a production system before applying these changes. This paper presents the architecture of Database Replay as well as experimental results that demonstrate its usefulness as testing methodology.

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This demonstration presents Oracle Database Replay, a novel approach to testing changes to the relational database management system component of an information system (software upgrades, hardware changes etc). Database Replay makes it possible to subject a test system to a real production workload, which helps identify all potential problems before implementing the planned changes on the production system. Any interesting workload period of a production database system can be captured with minimal overhead. The captured workload is used to drive a test system while maintaining the concurrency and load characteristics of the real production workload. The demonstration showcases how important maintaining the concurrency and load characteristics of the real workload is. The current testing solutions do not allow for synchronization based on data dependencies. Without proper synchronization the demonstration workload does not perform the work required and does not exercise the test system appropriately, leading to poor coverage and inadequate load. Thus many issues remain undetected. Database replay with its data based synchronization makes testing realistic and leads to the discovery of potential problems.

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Oracle Database Replay has been recently introduced in Oracle 11g as a novel tool to test relational database systems [9]. It involves recording the workload running on the database server in a production system, and subsequently replaying it on the database server in a test system. A key feature of workload replay that enables realistic reproduction of a real workload is synchronization. It is a mechanism that enforces specific ordering on the replayed requests that comprise the workload. It affects the level of request concurrency and the consistency of the replay results when compared to the captured workload. In this paper, we define the class of consistent replay synchronization schemes and study, for the first time, the spectrum they cover and the tradeoffs they present. We place the only scheme proposed so far [9], the one implemented in Oracle 11g Release 1, within the aforementioned spectrum and show that it is coarse-grained and more restrictive than necessary, often enforcing dependencies between calls that are independent. By enforcing needless waits, it decreases the level of possible concurrency and degrades performance. To overcome these drawbacks, we identify the best scheme within the spectrum; it is finer-grained than its counterparts and strikes the right balance across different tradeoffs: it enforces a partial ordering on the replayed calls that minimizes the number of required waits and maximizes the level of concurrency, without compromising consistency of the replay results. We have implemented the new scheme in Oracle 11g Release 2. Our experiments indicate that it produces better quality replays than the pre-existing one for major classes of workload.