Database
Files:
SQL Server databases have
three types of files:
· Primary
data files:
The primary data file is the
starting point of the database and points to the Page1 other files in the
database.
Every database has one primary
data file.
The recommended file name
extension for primary data files is .mdf.
· Secondary
data files:
Secondary data files are the data
files.
A database can have one or more
data files.
Secondary data files are other
than primary data file.
The recommended file name
extension for secondary data files is .ndf.
· Log
files
Log files hold all the log
information that is used to recover the database.
There must be at least one log
file for each database, although there can be
more than one.
The locations
of all the files in a database are recorded in the primary file of the database
and in the master database.
The
Database Engine uses the file location information from the master database
most of the time.
Logical
and Physical File Names
They
are:
1.logical_file_name2.Physical
file name (os_file_name)
Logical_file_name:
The logical_file_name is the name
used to refer to the physical file in all Transact-SQL statements.
Physical
file name (os_file_name)
The os_file_name is the name of
the physical file including the directory path.
SQL Server data and log files can
be put on either FAT or NTFS file systems. NTFS is recommended for the security
aspects of NTFS.
When multiple instances of SQL
Server are run on a single computer, each instance receives a different default
directory to hold the files for the databases created in the instance.
EX:
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