dbcc shrinkfile 例子 -回复
DBCC SHRINKFILE is a Transact-SQL command in SQL Server that allows you to shrink the size of a data or log file. In this article, we will discuss the usage and examples of the DBCC SHRINKFILE command, step by step.
Before we dive into the details, it is essential to understand the purpose of shrinking a file. Shrinking a file reduces its physical size on the disk, which can help reclaim disk space or optimize performance. However, it is important to note that shrinking a file can have adverse effects on performance and should be used judiciously.
Now, let's explore the step-by-step process of using the DBCC SHRINKFILE command.
Step 1: Understanding the Syntax
The syntax for the DBCC SHRINKFILE command is as follows:
DBCC SHRINKFILE ( {file_name  file_id} {, target_size} )
-
file_name: specifies the logical name of the file to be shrunk.
- file_id: specifies the ID of the file to be shrunk.
- target_size: specifies the desired target size for the file.
Step 2: Checking File Size and Free Space
Before shrinking a file, it is essential to understand the current size and the amount of free space within the file. This information can help determine an appropriate target size for the shrink operation. You can use the following query to retrieve this information:
sql
USE [database_name];
GO
DBCC SQLPERF(logspace);
This query will provide details about the current size, allocated space, and the percentage of free space in log files.
Step 3: Shrinking a Data File
To shrink a data file, you can use the following command:
sql
DBCC SHRINKFILE (N'data_file_logical_name', target_size);
Replace `data_file_logical_name` with the logical name of the data file you want to shrink and `target_size` with the desired size in megabytes (MB).
Step 4: Shrinking a Log File
To shrink a log file, you can use the following command:
sql
DBCC SHRINKFILE (N'log_file_logical_name', target_size);
Replace `log_file_logical_name` with the logical name of the log file you want to shrink and `target_size` with the desired size in megabytes (MB).
Step 5: Monitoring the Shrink Operation
Once the DBCC SHRINKFILE command is executed, the file shrink operation is initiated. You can monitor the progress of the operation using the `COMPLETE` and `PHYSLOCATIONS` virtual file stats:
sql
SELECT *
FROM sys.dm_exec_requests
WHERE command LIKE 'DBCC'
truncated data
This query will provide information about the percentage completed and the number of physical pages processed during the shrink operation.
Step 6: Shrinking TempDB Files
It is also possible to shrink the TempDB files using the DBCC SHRINKFILE command. However, it is recommended to avoid shrinking TempDB files frequently, as it can degrade performance.
To shrink TempDB data or log files, use the following syntax:
sql
USE master;
GO
DBCC SHRINKFILE (logical_name, target_size);
Replace `logical_name` with the logical name of the TempDB file you want to shrink and `target_size` with the desired size in megabytes (MB).
Step 7: Best Practices and Considerations
While the DBCC SHRINKFILE command can be useful, it is important to keep the following best practices and considerations in mind:
- Shrinking files should be done with caution and only when necessary, as it can lead to file fragmentation and can negatively impact performance.
- It is recommended to monitor the progress of the shrink operation to ensure it is completed successfully.

版权声明：本站内容均来自互联网，仅供演示用，请勿用于商业和其他非法用途。如果侵犯了您的权益请与我们联系QQ:729038198，我们将在24小时内删除。