A SQL Server database makes use of two types of files. Data is first stored in a transaction log, which is one type of file, and then subsequently written to the second type, the database file. When a user enters a transaction, the data she inserts, updates, or deletes is sent along to the RDBMS engine, which records that line of data in the transaction log.
Primary Data Files
The primary data file contains the startup information for the database and points to the other files in the database. User data and objects can be stored in this file or in secondary data files. Every