The first page in each file is a file header and the following few pages contain system information. Database boot page contains database attributes is stored in the first log file and in the primary data file. Each file grows by growth increments, as defined by user. File size increases every time it is filled with information. It is also necessary to specify the maximum file size, otherwise the file will grow until it has used all free space on the disk. Every database has only one primary data file from which all other files in the database start.
Locations of all data files in the database are recorded not only in the master database but also in the primary data file. Secondary data file. This type of data file includes all data files other than the primary data files. File extensions related to database management systems and database file types.
List of common database related files. Database is a collection of logically related records or files consolidated into a common pool that provides data for one or multiple uses. Databases can be classified according to types of content: bibliographic, full-text, numeric, and image.
The data in a database is organized according to a database model. A database model or database schema is the structure or format of a database , described in the formal language supported by the database management system. At a minimum, every SQL Server database has two operating system files: a data file and a log file.
Data files contain data and objects such as tables, indexes, stored procedures, and views. Log files contain the information that is required to recover all transactions in the database. Data files can be grouped together in filegroups for allocation and administration purposes. For example, a simple database named Sales has one primary file that contains all data and objects and a log file that contains the transaction log information.
A more complex database named Orders can be created that includes one primary file and five secondary files. The data and objects within the database spread across all six files, and the four log files contain the transaction log information. By default, the data and transaction logs are put on the same drive and path to handle single-disk systems.
This choice may not be optimal for production environments. We recommend that you put data and log files on separate disks. The logical file name must comply with the rules for SQL Server identifiers and must be unique among logical file names in the database.
It must follow the rules for the operating system file names. Only read-only databases and read-only secondary filegroups are allowed to be put on an NTFS compressed file system. For space savings, it is highly recommended to use data compression instead of file system compression.
When multiple instances of SQL Server are running on a single computer, each instance receives a different default directory to hold the files for the databases created in the instance.
Pages in a SQL Server data file are numbered sequentially, starting with zero 0 for the first page in the file. Each file in a database has a unique file ID number. To uniquely identify a page in a database, both the file ID and the page number are required. The following example shows the page numbers in a database that has a 4-MB primary data file and a 1-MB secondary data file. A file header page is the first page that contains information about the attributes of the file.
Several of the other pages at the start of the file also contain system information, such as allocation maps. One of the system pages stored in both the primary data file and the first log file is a database boot page that contains information about the attributes of the database.
SQL Server files can grow automatically from their originally specified size. When you define a file, you can specify a specific growth increment. Every time the file is filled, it increases its size by the growth increment.
If there are multiple files in a filegroup, they won't autogrow until all the files are full. For more information about pages and page types, see Pages and Extents Architecture Guide.
Each file can also have a maximum size specified.
0コメント