An Office Data Connection (ODC) is a persistent set of data connection settings that can be stored in an Office Excel 2007 workbook or in SharePoint Server for use in multiple workbooks. ODCs allow users to create their own queries into databases in the organization and to extract data and display it in their Office Excel 2007 workbooks. Although it is possible to query any database table and display the results in a workbook using an ODC, dynamic tables derived from standard databases are not supported by Excel Calculation Services. Excel Calculation Services can only refresh and display data derived from an Analysis Services query.
Because access to organizational data should be protected at all times, it is recommended that those ODCs that are approved for use by users be stored in a Data Connection Library. A Data Connection Library is a list that can store ODC files and can be referenced by users who need to use those ODCs to access data. The advantage of using a centralized library for ODC files is that, if any of the connection information related to the data source changes, then only one file needs to be updated. As a security control over ODC files, you must explicitly trust a Data Connection Library for Excel Calculation Services to be able to refresh the connection.
Open Central Administration from the Start menu.
Click the link for the Shared Services Provider.
Under Excel Services Settings, click Trusted Data Connection Libraries.
Click Add Trusted Data Connection Library.
Type in the URL address of the Data Connection Library you want to add and, optionally, add a description.