DBCC DROPCLEANBUFFERS (Transact-SQL)

**APPLIES TO:** SQL Server (starting with 2008) Azure SQL Database Azure SQL Data Warehouse Parallel Data Warehouse

Removes all clean buffers from the buffer pool, and columnstore objects from the columnstore object pool.

Transact-SQL Syntax Conventions

Syntax

Syntax for SQL Server:

DBCC DROPCLEANBUFFERS [ WITH NO_INFOMSGS ]  

Syntax for Azure SQL Warehouse and Parallel Data Warehouse:

DBCC DROPCLEANBUFFERS ( COMPUTE | ALL ) [ WITH NO_INFOMSGS ]  

Arguments

WITH NO_INFOMSGS
Suppresses all informational messages. Informational messages are always suppressed on SQL Data Warehouse and SQL Data Warehouse Parallel Data Warehouse

COMPUTE
Purge the data cache in memory from each Compute node.

ALL
Purge the data cache in memory from each Compute node and from the Control node. This is the default if you do not specify a value.

Remarks

Use DBCC DROPCLEANBUFFERS to test queries with a cold buffer cache without shutting down and restarting the server. To drop clean buffers from the buffer pool and columnstore objects from the columnstore object pool, first use CHECKPOINT to produce a cold buffer cache. This forces all dirty pages for the current database to be written to disk and cleans the buffers. After you do this, you can issue DBCC DROPCLEANBUFFERS command to remove all buffers from the buffer pool.

Result Sets

DBCC DROPCLEANBUFFERS on SQL Server returns:

DBCC execution completed. If DBCC printed error messages, contact your system administrator.  

Permissions

Applies to: SQL Server, Parallel Data Warehouse

• Requires membership in the sysadmin fixed server role.

Applies to: Azure SQL Data Warehouse

• Requires membership in the DB_OWNER fixed server role.

See Also

DBCC (Transact-SQL)
CHECKPOINT (Transact-SQL)