This guide is designed to highlight the solution for enabling security trimming on search results in SharePoint 2010 for external database. It also focuses on large datasets and file system crawling. It provides an overview of the requirement, a solution for the same, and concludes with implementation of the solution suggested. In order to have item level security implemented and search result trimming based on security, we need to have the security descriptor generated for each record and present in the table for each row. BCS is used to pull data and index in SharePoint for implementing search driven applications, we need constant updation of data from the external system. In such systems we need incremental update to work to ensure CRUD operations. If you have documents stored in your External Systems then it is possible using the Business Connectivity Services (BCS) give your end users the ability to access and crawl these artifacts with ease. The Stream Accessor method allows you to pull System.Byte data from your External System and make it available from within SharePoint.