SQL Server 2000 Database File Types

Data Files and Transaction Logs

SQL Server utilizes two main files to store data and transactions on disks.

Data File (.mdf or .ndf extensions by default) – This is the physical storage for all of the data on disk. Pages are read into the buffer cache when users request data for viewing or modification. After data has been modified in memory (the buffer cache), it is written back to the data file.

Transaction Log (.ldf extension by default) – The transaction log records the modifications that have occurred in the database as well as the transactions that caused the modifications. Information that was in memory within the log cache is ultimately stored in the Transaction log.

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