SSIS Data Source Views or DSVs designed to create logical views of your data. SSIS DSVs can be shared across your SSIS projects. Moreover, SSRS can utilize same DSVs as well. They usually contain tables, views, SPs and user queries. They are useful in several ways. For example, DSVs can be used to map unfriendly system fields to more friendly and readable formats. SSIS Data Source Views can also be used to establish relationships between tables that may not exist in physical schema.
It is also useful in segmentation of large database into more manageable chunks of data based on business function or security paradigm. SSIS Data Source Views also help with labeling field names to more user friendly names.
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SSIS Data Source Views can be reused multiple times and across SSIS packages. There is one problem with SSIS Data Source Views though. Once they are created they cannot be refreshed automatically if underling data schema is changed and manual update is required. SSIS Data Source Views are also helpful in SSIS Package development. They allow keeping schema stable and with the help of cached data you are not dependent on your original data source. Having smaller subset of your underlying data, makes SSIS Package development off DSVs more efficient as well.