收缩数据库Shrink a Database

03/14/2017

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适用于：Applies to: SQL ServerSQL Server(所有支持的版本)SQL ServerSQL Server (all supported versions) Azure SQL 数据库Azure SQL DatabaseAzure SQL 数据库Azure SQL Database适用于：Applies to: SQL ServerSQL Server(所有支持的版本)SQL ServerSQL Server (all supported versions) Azure SQL 数据库Azure SQL DatabaseAzure SQL 数据库Azure SQL Database

本主题说明如何使用 SQL Server 2019 (15.x)SQL Server 2019 (15.x) 或 SQL Server Management StudioSQL Server Management Studio 在 Transact-SQLTransact-SQL中使用对象收缩数据库。This topic describes how to shrink a database by using Object in SQL Server 2019 (15.x)SQL Server 2019 (15.x) by using SQL Server Management StudioSQL Server Management Studio or Transact-SQLTransact-SQL.

收缩数据文件通过将数据页从文件末尾移动到更靠近文件开头的未占用的空间来恢复空间。Shrinking data files recovers space by moving pages of data from the end of the file to unoccupied space closer to the front of the file. 在文件末尾创建足够的可用空间后，可以取消对文件末尾的数据页的分配并将它们返回给文件系统。When enough free space is created at the end of the file, data pages at end of the file can be deallocated and returned to the file system.

本主题内容In This Topic

开始之前Before You Begin

限制和局限Limitations and Restrictions

收缩后的数据库不能小于数据库的最小大小。The database cannot be made smaller than the minimum size of the database. 最小大小是在数据库最初创建时指定的大小，或是上一次使用文件大小更改操作(如 DBCC SHRINKFILE)设置的显式大小。The minimum size is the size specified when the database was originally created, or the last explicit size set by using a file-size-changing operation, such as DBCC SHRINKFILE. 例如，如果数据库最初创建时的大小为 10 MB，后来增长到 100 MB，则该数据库最小只能收缩到 10 MB，即使已经删除数据库的所有数据也是如此。For example, if a database was originally created with a size of 10 MB and grew to 100 MB, the smallest size the database could be reduced to is 10 MB, even if all the data in the database has been deleted.

不能在备份数据库时收缩数据库。You cannot shrink a database while the database is being backed up. 反之，也不能在数据库执行收缩操作时备份数据库。Conversely, you cannot backup a database while a shrink operation on the database is in process.

建议Recommendations

若要查看数据库中当前的可用(未分配)空间量。To view the current amount of free (unallocated) space in the database.

当您计划收缩数据库时，请考虑以下信息：Consider the following information when you plan to shrink a database:

在执行会产生许多未使用空间的操作(如截断表或删除表操作)后，执行收缩操作最有效。A shrink operation is most effective after an operation that creates lots of unused space, such as a truncate table or a drop table operation.

大多数数据库都需要一些可用空间，以供常规日常操作使用。Most databases require some free space to be available for regular day-to-day operations. 如果反复收缩数据库并注意到数据库大小变大，则表明收缩的空间是常规操作所必需的。If you shrink a database repeatedly and notice that the database size grows again, this indicates that the space that was shrunk is required for regular operations. 在这种情况下，反复收缩数据库是一种无谓的操作。In these cases, repeatedly shrinking the database is a wasted operation.

收缩操作不会保留数据库中索引的碎片状态，通常还会在一定程度上增加碎片。A shrink operation does not preserve the fragmentation state of indexes in the database, and generally increases fragmentation to a degree. 这是不要反复收缩数据库的另一个原因。This is another reason not to repeatedly shrink the database.

除非有特定要求，否则不要将 AUTO_SHRINK 数据库选项设置为 ON。Unless you have a specific requirement, do not set the AUTO_SHRINK database option to ON.

SecuritySecurity

权限Permissions

要求具有 sysadmin 固定服务器角色或 db_owner 固定数据库角色的成员身份。Requires membership in the sysadmin fixed server role or the db_owner fixed database role.

使用 SQL Server Management StudioUsing SQL Server Management Studio

收缩数据库To shrink a database

在 对象资源管理器 中，连接到 SQL Server 数据库引擎SQL Server Database Engine的实例，然后展开该实例。In Object Explorer, connect to an instance of the SQL Server 数据库引擎SQL Server Database Engine, and then expand that instance.

展开“数据库”，再右键单击要收缩的数据库。Expand Databases, and then right-click the database that you want to shrink.

指向 “任务” ，指向 “收缩” ，然后单击 “数据库” 。Point to Tasks, point to Shrink, and then click Database.

DatabaseDatabase

显示所选数据库的名称。Displays the name of the selected database.

当前分配的空间Current allocated space

显示所选数据库的总已用空间和未使用空间。Displays the total used and unused space for the selected database.

可用空间Available free space

显示所选数据库的日志和数据文件中可用空间的总和。Displays the sum of free space in the log and data files of the selected database.

在释放未使用的空间前重新组织文件Reorganize files before releasing unused space

选择此选项等效于执行指定了目标百分比选项的 DBCC SHRINKDATABASE。Selecting this option is equivalent to executing DBCC SHRINKDATABASE specifying a target percent option. 清除此选项等效于执行带 TRUNCATEONLY 选项的 DBCC SHRINKDATABASE。Clearing this option is equivalent to executing DBCC SHRINKDATABASE with TRUNCATEONLY option. 在打开对话框时，默认情况下不选择此选项。By default, this option is not selected when the dialog is opened. 如果选择此选项，用户必须指定目标百分比选项。If this option is selected, the user must specify a target percent option.

收缩后文件中的最大可用空间Maximum free space in files after shrinking

输入在数据库收缩后数据库文件中剩余可用空间的最大百分比。Enter the maximum percentage of free space to be left in the database files after the database has been shrunk. 值可以介于 0 和 99 之间。Permissible values are between 0 and 99.

单击“确定”。Click OK.

使用 Transact-SQLUsing Transact-SQL

收缩数据库To shrink a database

连接到 数据库引擎Database Engine。Connect to the 数据库引擎Database Engine.

在标准菜单栏上，单击 “新建查询” 。From the Standard bar, click New Query.

将以下示例复制并粘贴到查询窗口中，然后单击“执行” 。Copy and paste the following example into the query window and click Execute. 此实例使用 DBCC SHRINKDATABASE 减少 UserDB 数据库中数据文件和日志文件的大小并允许数据库中有 10 ％ 的可用空间。This example uses DBCC SHRINKDATABASE to decreases the size of the data and log files in the UserDB database and to allow for 10 percent free space in the database.

DBCC SHRINKDATABASE (UserDB, 10);

GO

跟进：在收缩数据库之后Follow Up: After you shrink a database

被移动用来收缩文件的数据可以分布到文件的任何可用位置。Data that is moved to shrink a file can be scattered to any available location in the file. 这将导致索引碎片并使搜索索引范围的查询变慢。This causes index fragmentation and can slow the performance of queries that search a range of the index. 若要消除碎片，请考虑在收缩后重新生成文件的索引。To eliminate the fragmentation, consider rebuilding the indexes on the file after shrinking.

另请参阅See Also