What is MDF, NDF, and LDF ?

In Microsoft SQL Server, all your significant and business-critical data is stored in a database, in the form of tables. Microsoft SQL Server database can be accessed using the queries. A query can be in T-SQL (Transaction- Structured Query Language). The SQL Server database is made up of a number of components and files. All these files are required to be in working state for proper functioning of the database and accessing of your mission-critical data. The most useful database files are- MDF (Master Database File), NDF (Next Data File), and LDF (Log Data File).

• MDF File- It is the main data file of Microsoft SQL Server database. All your significant data is stored in this file. The extension of master database file is .mdf. This is the start point of MS SQL Server database and the starting point to other database files. Each database has at least one primary data file. MDF file is directly accessible by the user. You can store and retrieve data from this database file using T-SQL queries.
  
  Purpose of MDF File- The main application of this database file is store your valuable data in an organized form. It creates index of the stored data to make it easily accessible and improve SQL Server performance.


• NDF File- This is the secondary data file of Microsoft SQL Server database, stored with .ndf extension. It comprise of all the data files, other than primary database file. A database can have either or more secondary data files.
  
  Purpose of NDF File- The main function of the NDF or secondary data file is to store optional metadata of Microsoft SQL Server database. The metadata is used for the internal processing of the database and data management.


• LDF File- These files store log information of SQL Server database. The log or transaction log files are used to check database processing and recover Microsoft SQL Server database. Every database contains at least one log file for every database, though the number of log files can be more than one.
  
  Purpose of LDF File- It stores history of the operations performed on SQL Server database. It helps the administrator to guarantee the ACID (Atomicity, Consistency, Isolation, Durability) properties over hardware failure or system crashes.

All these database files are extremely critical for the operations of SQL Server. Over time, these database files get damaged due to various reasons, like virus infection, application malfunction, system crash, and other similar reasons. At this point, SQL Server recovery is required to repair and restore the damaged database.

Stellar Phoenix SQL Recovery software helps you to effectively recover SQL Server database in all cases of corruption. This SQL recovery utility is designed for Microsoft SQL Server 2008, 2005, and 2000. The software successfully restores all SQL Server database objects, such as tables, reports, forms, macros, triggers, data types, stored procedures. It retrieves MDF (Master Database File) and NDF (Next Data File) from a damaged database.