If you are
working on SQL related concepts, then there would be high chances of you coming
across .mdf, .ndf and .ldf files. These are files nothing but primary data files,
secondary data files, and logical files.
Primary Data File
The Primary
data file is the .mdf file, where all the objects such as tables, views, triggers,
stored procs, functions, etc., are stored. There is always just one .mdf file for
a database. Further, every database should consist of a starting point and this
is handled by the primary file. The primary file is held responsible for
pointing the other files of a database. .mdf files are stored in the physical
storage drive of the computer.
Example:
<database_name>.mdf
Secondary Data File
A secondary data file is held responsible to hold all the data apart from the one
handled by the primary data file. There are places where no secondary data
files are present for a database. However, the majority of times, there are two
secondary data files present in a database. Similar to primary files, the
secondary files are as well stored in the physical storage drive of the
computer.
Example:
<database_name>.ndf
Log File
The log
files hold the logical information of a database. It helps in recovering the
database. A database can have one or more log files. The log files as well are
stored in the local machine. Usually, log file sizes allotted in either a physical drive or mount drive can increase due to an increased transaction in the database.
It can further be shrunk with special queries.
Example:
<database_name>.ldf
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