Expert Oracle Exadata - Parent Directory

CHAPTER 1 WHAT IS EXADATA?end of the chapter, you should have a pretty good feel for how all the pieces fit together and a basicunderstanding of how Exadata works. The rest of the book will provide the details to fill out the skeletonthat is built in this chapter. Kevin Says: In my opinion, Data Warehousing / Business Intelligence practitioners, in an Oracle environment,who are interested in Exadata, must understand Cell Offload Processing fundamentals before any other aspect ofthe Exadata Database Machine. All other technology aspects of Exadata are merely enabling technology in supportof Cell Offload Processing. For example, taking too much interest, too early, in Exadata InfiniBand componentry issimply not the best way to build a strong understanding of the technology. Put another way, this is one of the rarecases where it is better to first appreciate the whole cake before scrutinizing the ingredients. When I educate onthe topic of Exadata, I start with the topic of Cell Offload Processing. In doing so I quickly impart the following fourfundamentals:Cell Offload Processing: Work performed by the storage servers that would otherwise have to be executed in thedatabase grid. It includes functionality like Smart Scan, data file initialization, RMAN offload, and Hybrid ColumnarCompression (HCC) decompression (in the case where In-Memory Parallel Query is not involved).Smart Scan: The most relevant Cell Offload Processing for improving Data Warehouse / Business Intelligencequery performance. Smart Scan is the agent for offloading filtration, projection, Storage Index exploitation, andHCC decompression.Full Scan or Index Fast Full Scan: The required access method chosen by the query optimizer in order to triggera Smart Scan.Direct Path Reads: Required buffering model for a Smart Scan. The flow of data from a Smart Scan cannot bebuffered in the SGA buffer pool. Direct path reads can be performed for both serial and parallel queries. Direct pathreads are buffered in process PGA (heap).An Overview of ExadataA picture’s worth a thousand words, or so the saying goes. Figure 1-1 shows a very high-level view of theparts that make up the Exadata Database Machine.2