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Connections and Remote Database Access-Chapter 16

DOI: 10.1016/b978-155860456-8/50017-5


Publisher Summary This chapter discusses the relationship of sessions and connections to software applications. SQL: 1999 recognizes that other actions may have to take place, such as establishing context for database execution, before the Database Management Systems (DBMS) can even be aware that it has been given a task to do. In some implementations, the context exists because the DBMS runtime code was linked with the server/client application. In others, the context is established by execution of implementation-defined statements to connect the application program with DBMS. In still others, system variables set up the context. SQL: 1999 resolves this issue by defining several statements that application programs use to control connections to DBMS's and by specifying the default behavior much more thoroughly than its predecessors. The chapter focuses on three statements, such as CONNECT, SET CONNECTION, and DISCONNECT, that are used for manipulating these connections. There is another ISO standard, called Remote Database Access (RDA), related to connections to the SQL database systems. This standard defines protocols and services for accessing databases over network connections. RDA allows the user to execute a significant fraction of the available SQL statements, but not all of them. The limitation is caused mostly by the fact that the RDA standard is inherently dynamic in nature, so some statements are not supported because of the obvious redundancy, such as the dynamic SQL statements themselves. The chapter briefly describes RDA and ends with a discussion on termination statement as well as connections.

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