Returns information about all the data pages that are currently in the SQL Server buffer pool. The output of this view can be used to determine the distribution of database pages in the buffer pool according to database, object, or type.
When a data page is read from disk, the page is copied into the SQL Server buffer pool and cached for reuse. Each cached data page has one buffer descriptor. Buffer descriptors uniquely identify each data page that is currently cached in an instance of SQL Server. sys.dm_os_buffer_descriptors returns cached pages for all user and system databases. This includes pages that are associated with the Resource database.
database_id
int
ID of database associated with the page in the buffer pool. Is nullable.
file_id
int
ID of the file that stores the persisted image of the page. Is nullable
page_id
int
ID of the page within the file. Is nullable.
page_level
int
Index level of the page. Is nullable
allocation_unit_id
bigint
ID of the allocation unit of the page. This value can be used to join sys.allocation_units. Is nullable.
Note sys.dm_os_buffer_descriptors might show nonexistent values in allocation_unit_id for clustered indexes that are created in versions of SQL Server earlier than SQL Server 2005.
page_type
nvarchar(60)
Type of the page, such as: Data page or Index page. Is nullable. For more information, see Understanding Pages and Extents.
row_count
int
Number of rows on the page. Is nullable.
free_space_in_bytes
int
Amount of available free space, in bytes, on the page. Is nullable.
is_modified
bit
1 = Page has been modified after it was read from the disk. Is nullable.
numa_node
int
Nonuniform Memory Access node for the buffer.
PermissionsRequires VIEW SERVER STATE permission on the server.
sys.dm_os_buffer_descriptors returns pages that are being used by the Resource database. sys.dm_os_buffer_descriptors does not return information about free or stolen pages, or about pages that had errors when they were read.
sys.dm_os_buffer_descriptors
sys.databases
database_id
many-to-one
sys.dm_os_buffer_descriptors
<userdb>.sys.allocation_units
allocation_unit_id
many-to-one
sys.dm_os_buffer_descriptors
<userdb>.sys.database_files
file_id
many-to-one
Examples A. Returning cached page count for each databaseThe following example returns the count of pages loaded for each database.
SELECT count(*)AS cached_pages_count
,CASE database_id
WHEN 32767 THEN 'ResourceDb'
ELSE db_name(database_id)
END AS Database_name
FROM sys.dm_os_buffer_descriptors
GROUP BY db_name(database_id) ,database_id
ORDER BY cached_pages_count DESC;
The following example returns the count of pages loaded for each object in the current database.
SELECT count(*)AS cached_pages_count
,name ,index_id
FROM sys.dm_os_buffer_descriptors AS bd
INNER JOIN
(
SELECT object_name(object_id) AS name
,index_id ,allocation_unit_id
FROM sys.allocation_units AS au
INNER JOIN sys.partitions AS p
ON au.container_id = p.hobt_id
AND (au.type = 1 OR au.type = 3)
UNION ALL
SELECT object_name(object_id) AS name
,index_id, allocation_unit_id
FROM sys.allocation_units AS au
INNER JOIN sys.partitions AS p
ON au.container_id = p.partition_id
AND au.type = 2
) AS obj
ON bd.allocation_unit_id = obj.allocation_unit_id
WHERE database_id = db_id()
GROUP BY name, index_id
ORDER BY cached_pages_count DESC;
RetroSearch is an open source project built by @garambo | Open a GitHub Issue
Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo
HTML:
3.2
| Encoding:
UTF-8
| Version:
0.7.4