April 24th, 2012 by Michael Rainey
Before I jump into the first of two posts discussing change data capture with Oracle GoldenGate and Oracle Data Integrator 11g, I would like to first introduce myself. My name is Michael Rainey and I am the newest member of the Rittman Mead America team, joining just last month as an ODI consultant. I have been working with Oracle Data Integrator 11g since it was first released, and was part of a team at my former employer, Pacific Northwest National Laboratory, who developed an innovative solution for the rapid migration of SQL-based metadata to ODI Interfaces through use of the ODI SDK. I was able to present a brief overview of our solution at Oracle OpenWorld 2011 in a Customer Perspectives session. I plan on sharing some of my knowledge with you regarding data integration through this blog, and hopefully some future conference sessions. But, enough about me, on to the real topic of this post, Extreme BI: Capturing Change with Oracle GoldenGate and ODI.
A few months back, Stewart Bryson described the need for a real-time data warehousing solution for loading the Foundation Layer with raw source data changes in a blog post titled Agile Data Warehousing with Exadata and OBIEE: Puzzle Pieces. As he described the importance of the Foundation Layer in delivering Extreme BI, he noted that Oracle GoldenGate, though a powerful and flexible replication technology, is lacking a simple setup for tracking source data changes in the data warehouse. He also noted that there may be a workaround available with some Oracle GoldenGate configuration and a little coding, and alluded to a potential future blog post (which you are now reading). What follows is one approach to solving this problem, using Oracle Data Integrator (ODI) 11g and Oracle GoldenGate (OGG).
First, a little background on the Oracle Next-Generation Reference DW Architecture and what we are trying to accomplish. An excellent description to help further your understanding is laid out by Mark Rittman here. As Mark describes it, the Staging layer is a “landing pad” for a current version of the source data gathered into the data warehouse. It is the source for Extract, Load, and Transform (ELT) processes that move data to the Performance and Access layer, often using a tool such as ODI or Oracle Warehouse Builder (OWB). The Foundation layer, on the other hand, is a 3NF representation of data from all source databases. It represents the detailed history of all source transactions, enabling drill-through from the Performance layer for transactional data lookup. This layer also allows for changing star schema requirements to be readily implemented, as the source transaction history has been stored since the data warehouse inception.
The goal is to implement a real-time data replication process that will support Extreme BI, not only loading the current rows to Staging through to the Performance Layer, but also pushing the raw source data to the Foundation Layer, and capturing all transaction history. A typical misconception is that we must load the Staging from the Source first, then build the Foundation layer history from Staging. While this may look good in theory, the reality is that you must duplicate your effort when implementing the physical mappings from Source → Staging, and then again from Staging → Foundation. In order to increase the speed of development and remain an Agile data warehouse project, we must capture the changes to the raw source transaction data as they occur.
Our solution begins with Oracle GoldenGate and its real-time replication capabilities, integrating with Oracle Data Integrator 11g and its journalizing change data capture implementation. The setup will be as follows, with the replication from GoldenGate loading both Staging and Foundation layers, and then the ODI CDC moving data through Staging into the Performance layer. In this series of posts, we’ll focus on the replication piece, saving the Performance layer load for another time.
The next post will dig into the details of my solution, focusing on the integration between GoldenGate and ODI, and the modifications necessary for Extreme BI data warehousing.