数据库压缩2（Database compression 2）.doc

数据库压缩2（Database compression 2） DBCC SHRINKDATABASE Shrinks the size of the data file specified in the database. grammar DBCC SHRINKDATABASE (database_name [[target_percent]] [TRUNCATEONLY] |, {NOTRUNCATE} ) parameter Database_name Is the name of the database to be contracted. The database name must conform to the rules of identifiers. For more information, see using identifiers. Target_percent Is the amount of space available in the database file after the database shrinks. NOTRUNCATE Causes the reserved file space to be kept in the database file. If not specified, the released file space is released to the operating system. TRUNCATEONLY This results in the release of any unused space in the data file to the operating system and shrinks the file to the last allocated size, thus reducing the size of the file without moving any data. Rows that do not attempt to reposition an unassigned page. When using TRUNCATEONLY, ignore target_percentis. Notes Microsoft, SQL, Server? Can shrink: All data and log files for a particular database. Execute DBCC SHRINKDATABASE. Data or log files at a time in a particular database. Execute DBCC SHRINKFILE. DBCC SHRINKDATABASE shrinks the data files in each file. However, when DBCC SHRINKDATABASE shrinks the log file, it looks as if all the log files are in a continuous log pool. Suppose the database named mydb has two data files and two log files. These data files and log files are 10 MB in size. The first data file contains 6 MB data. For each file, SQL Server calculates the target size, that is, the size of the file to be contracted. When specifying DBCC SHRINKDATABASE with target_percent, the target size of SQL Server is the size of the target_percent space available in the contracted file. For example, if specified, press target_percent 25 to shrink mydb. The target size of the file calculated by SQL Server is 8 MB (6 MB data plus 2 MB of free space). Therefore, SQL Server moves any data from the last 2 MB of the data file to the ava