Business Connectivity Services (BCS) is an evolution of Business Data Catalog (BDC) in MOSS 2007. BDC used to provide an access to content external to SharePoint in a read-only mode. There was no way to do bi-directional data access. BCS provides exactly the same. BCS can be used to access almost any kind of external systems like Oracle, Siebel etc. SharePoint Designer (SPD) 2010 allows to create this kind of access external content using to Web Services, WCF Services, .NET Assemblies. If external content cannot be used using any of these three methods, SPD cannot be used. BCS XML needs to modified in XML and integrate. At a very high-level BCS looks as under.
Some of the key features are as under.