Tham khảo tài liệu 'expert sql server 2008 development- p7', công nghệ thông tin, cơ sở dữ liệu phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | CHAPTER 9 DESIGNING SYSTEMS FOR APPLICATION CONCURRENCY Tip If you are interested in finding further statistics about the waits enforced by Resource Governor try looking for rows in the DMV where wait_type is RESMGR_THROTTLED. Summary Concurrency is a complex topic with many possible solutions. In this chapter I introduced the various concurrency models that should be considered from a business process and data collision point of view and explained how they differ from the similarly named concurrency models supported by the SQL Server database engine. Pessimistic concurrency is probably the most commonly used form but it can be complex to set up and maintain. Optimistic concurrency while more lightweight might not be so applicable to many business scenarios and multivalue concurrency control while a novel technique might be difficult to implement in such a way that allowing collisions will help deliver value other than a performance enhancement. Finally I covered an overview of how Resource Governor can balance the way in which limited resources are allocated between different competing requests in a concurrent environment. The discussion here only scratched the surface of the potential for this technique and I recommend that readers interested in the subject dedicate some time to further research this powerful feature. 281 C H A P T E R 10 Working with Spatial Data The addition of spatial capabilities was one of the most exciting new features introduced in SQL Server 2008. Although generally a novel concept for many SQL developers the principles of working with spatial data have been well established for many years. Dedicated geographic information systems GISs such as ARC INFO from ESRI have existed since the 1970s. However until recently spatial data analysis has been regarded as a distinct niche subject area and knowledge and usage of spatial data has remained largely confined within its own realm rather than being integrated with .
