[2].SSIS Objects and Process Control Components
Before you begin learning how to create SSIS applications, it is important to familiarize yourself first with the SSIS process control components and the objects used to create SSIS applications. The first object to note within SSIS is the package.
An SSIS package is the highest-level object within an SSIS application. A package is a discrete unit of work that you define for ETL operations or SQL Server Services administration operations or both. It is a collection of SSIS process control components and their objects that define the operations, process dependencies, and sequence flow of activities and operations required for a data integration application. Package objects include containers, tasks, precedence constraints, variables, data sources, data destinations, SQL Server administration functions, and custom tasks that you can create to address unique requirements for your applications. Package objects are applied to package process control components that include the control flow, data flow, and event handler.
To control the sequence of activities and operations within a package, you apply the precedence constraint object. Precedence constraints are defined between your package objects and are used to specify the order sequence of operations processing and to control processing branching among optional process flows, dependent data values, and conditions or error conditions.
Another useful object of a package is the container. A container is the package object used to group other objects and other containers. Common uses of containers are for performing iterative processing such as looping through a dataset or processing a set of data files within a directory. Although the container object is within a package, you can consider the SSIS package itself as a special high-level container.
SSIS objects also include a comprehensive set of transformation tasks that are important for data integration and BI solutions. These tasks are designed for merging or aggregating data and for converting and transforming data formats and types. Some new tasks have been provided for handling specialized BI operations such as managing slowly changing dimension data. You can also extend SSIS with your own custom tasks and transformations to handle unique requirements within your business application systems environment.
Perhaps best of all, you will find that with all the SSIS objects available to you for package creation, you can create robust, high-performance ETL and data integration applications with no programming code required. By simply dragging and dropping containers, sources, destinations, transformations, and other objects, the SSIS designer automatically creates all the package executable code for you. Throughout the next several chapters, you will learn more about package objects and control components and practice with many of the objects available to design and develop SSIS packages.
一个SSIS包内的SSIS应用程序的最高级别的对象。包是一个离散的工作单位，您定义的ETL操作或SQL Server服务管理操作或两者。这是一个SSIS过程控制组件和它们的对象定义操作过程中的依赖关系，和序列数据集成应用程序所需的活动和操作流程的集合。包对象包括容器，任务优先约束，变量，数据源，数据目标，SQL Server管理功能，自定义任务，您可以创建您的应用程序，以解决独特的要求。包对象包过程控制元件，包括控制流，数据流和事件处理。
要控制在一个包内的活动和行动的顺序，你申请的优先约束对象。优先约束定义之间的包对象，用于指定的业务处理序和控制分支在可选的流程，相关的数据值，条件或错误条件的处理。
包的另一个有用的对象是容器。容器是用来包对象组中的其他对象和其他容器。容器常见的用途是进行迭代遍历数据集或处理目录内的一组数据文件，如处理。虽然是包内的容器对象，可以考虑作为一种特殊的高级别容器的SSIS包本身。
SSIS的对象还包括一套全面的改造任务，为数据集成和BI解决方案的重要。这些任务是专为合并或汇总数据，数据格式和类型转换和改造。已提供了一些新的任务来处理专门的BI业务，例如缓慢变化维度的数据管理。您还可以扩展自己的自定义任务和转换来处理您的业务应用系统的环境内的独特要求的SSIS。
也许最好的，你会发现，所有的SSIS包创建对象，你可以创建强大的，高性能的ETL和数据集成应用程序，无需编程代码。通过简单的拖放容器，来源，目的地，转换，和其他对象，SSIS设计器会自动为您创建所有包的可执行代码。整个接下来的几个章节中，您将学习包对象和控制元件和实践，有许多可用来设计和开发SSIS包的对象。
