Useful new DMV’s in SQL Server 2008 R2 SP1 and SQL Server 2012

Introduction

Microsoft SQL Server 2008 R2 and SP1 and SQL Server 2012 has a new set of DMVs that includes sys.dm_server_memory_dumps, sys.dm_server_registry, sys.dm_server_services, sys.dm_os_windows_info, sys.dm_os_volume_stats and sys.dm_exec_query_stats. These DMVs can be used to return the information about SQL Server configuration and installation, memory dumps related information and information that can be useful to diagnose problems and tune query performance.

In this article, I'll cover the purpose and use of these new DMVs of SQL Server 2008 R2 SP1 and SQL Server 2012 (DENALI):

1) sys.dm_server_memory_dumps - It contains the information about memory dumps files generated by the SQL Server Database Engine. It returns 3 columns listed as below:

Column Name Data type Description Attribute
filename nvarchar(256) Memory dump file name and path. NOT NULL
creation_time datetimeoffset(7) Date and time the file was created. NOT NULL
size_in_bytes bigint Size of the memory dump file in bytes. NULL

Usage:

USE [master]
GO

SELECT * FROM sys.dm_server_memory_dumps;
GO

Example:

Currently there are no memory dump files are available but if you see any on your SQL Server then alert your SQL Server DBA, because memory dumps can be serious and could lead to data corrouption and other problems.

Permissions:

Requires VIEW SERVER STATE permission on the server.

MSDN reference: http://technet.microsoft.com/en-us/library/hh204543.aspx

2) sys.dm_server_registry – This DMV contains the configuration and installation information for the current instance of SQL Server that is stored in Windows registry. This DMV returns one row per registry key. It returns 3 columns listed as below:

Column Name Data type Description Attribute
registry_key nvarchar(256) Stores name of registry key. NULL
value_name nvarchar(256) Stores the name of key value. In Windows Registry Editor this item is shown under Name column. NULL
value_data sql_variant Stores value of the key data. In Windows Registry Editor this item is shown under Data column. NULL

In old version of SQL Server you can access the Windows registry information via xp..regread. This DMV is use full if you want to audit the configuration of your SQL Server.

USE [master]
GO

SELECT * FROM sys.dm_server_registry;
GO

Example:

Permissions:

Requires VIEW SERVER STATE permission on the server.

MSDN reference: http://msdn.microsoft.com/en-us/library/hh204561.aspx

3) sys.dm_server_services – The initial version of this DMV that was released in SQL Server 2008 R2 SP1 only returns information about SQL Server and SQL Agent service. In SQL Server 2012 it also returns information about Full-text service.

This DMV returns one row per service. It returns 11 columns listed as below:

Column Name Data type Description Attribute
servicename nvarchar(256) Stores name of the SQL Server, Full-text or SQL Server Agent service. NOT NULL
startup_type int Indicates start mode of the SQL Server, Full-text or SQL Server Agent service.

Value Description
0 Other (boot start)
1 Other (system start)
2 Automatic
3 Manual
4 Disabled
NULL
startup_desc nvarchar(256) Describe the start mode of the SQL Server, Full-text or SQL Server Agent service.

Value Description
Other Other (boot start)
Other Other (system start)
Automatic Auto start
Manual Demand start
Disabled Disabled
NOT NULL
status int Indicates the existing status of the SQL Server, Full-text and SQL Agent service.

Value Description
1 Stopped
2 Other (start pending)
3 Other (stop pending)
4 Running
5 Other (continue pending)
6 Other (pause pending)
7 Paused

 

NULL
status_desc nvarchar(256) Describe the existing status of the SQL Server, Full-text and SQL Agent service.

Value Description
Stopped Service is currently stopped.
Other (start pending) Service is in the process of starting.
Other (stop pending) Service is in the process of stopping.
Running Service is currently running.
Other (continue pending) Service is in pending state.
Other (pause pending) Service is in the process of pausing.
Paused Service is currently paused.

 

NOT NULL
process_id int Stores the process id of the SQL Server, Full-text and SQL Agent service. NOT NULL
last_startup_time datetimeoffset(7) Stores the date and time when the SQL Server, Full-text and SQL Agent service was last started. NULL
service­_account nvarchar(256) Stores the account name of authorized account to control the service. NOT NULL
filename nvarchar(256) Stores the full OS path of service executable. NOT NULL
is_clustered nvarchar(1) Indicates whether the service is installed as a resource of the cluster server. NOT NULL
cluster_nodename nvarchar(256) Stores the names of the cluster nodes. NULL

In old versions of SQL Server you can access the same information by accessing the Windows registry information for the service via xp..regread. This DMV is useful if you want to audit the what services are installed as part of the SQL installation.

Usage:

USE [master]
GO

SELECT * FROM sys.dm_server_services;
GO

Example:

Permissions:

Requires VIEW SERVER STATE permission on the server.

MSDN reference: http://msdn.microsoft.com/en-us/library/hh204542.aspx

4) sys.dm_os_windows_info – The DMV returns detailed information about Windows OS version for example the release number, service pack level and language version of SQL Server Windows OS. This DMV returns only one row with four columns listed as below:

Column Name Data type Description Attribute
windows_release nvarchar(256) Stores the Windows OS release number. NOT NULL
windows_service_pack_level nvarchar(256) Store the service pack level of Windows operating system. NOT NULL
Windows_sku int Stores ID of Windows Socket Keeping Unit (SKU) NULL
os_language_version int Stores Windows locale identifier (LCID) of the operating system. NOT NULL

In old versions of SQL Server you can access the same information by accessing the Windows registry information for the OS via xp..regread.

Usage:

USE [master]
GO

SELECT * FROM sys.dm_os_windows_info;
GO

Example:

Permissions:

Requires VIEW SERVER STATE permission on the server.

MSDN reference: http://msdn.microsoft.com/en-us/library/hh204565.aspx

5) sys.dm_os_volume_stats – The DMV returns Windows OS volume information on which the database files resides. It takes two parameters i.e. database_id (ID of the database) and file_id (ID of the database file). This DMV returns 13 columns listed as below:

Column Name Data type Description Attribute
database_id int ID of the database. NOT NULL
file_id int ID of the file. NOT NULL
volume_mount_point nvarchar(512) Mount point at which the volume is rooted. Can return an empty string. NOT NULL
volume_id nvarchar(512) Operating system volume ID. Can return an empty string NOT NULL
logical_volume_name nvarchar(512) Logical volume name. Can return an empty string NOT NULL
file_system_type nvarchar(512) Type of file system volume (for example, NTFS, FAT, RAW). Can return an empty string NOT NULL
total_bytes bigint Total size of the volume in bytes. NOT NULL
available_bytes bigint Available free space on the volume in bytes. NOT NULL
supports_compression bit Indicates if the volume supports operating system compression. NOT NULL
supports_alternate_streams bit Indicates if the volume supports alternate streams. NOT NULL
supports_sparse_files bit Indicates if the volume supports sparse files. NOT NULL
is_read_only bit Indicates if the volume is currently marked as read only. NOT NULL
is_compressed bit Indicates if this volume is currently compressed. NOT NULL

In old versions of SQL Server you can access the same information by writing your own CLR procedure by using one of the .NET framework languages.

Usage:

USE [master]
GO

SELECT * FROM sys.dm_os_volume_stats (database_id, file_id);
GO

Example:

Permissions:

Requires VIEW SERVER STATE permission on the server.

MSDN reference: http://msdn.microsoft.com/en-us/library/hh223223.aspx

6) sys.dm_exec_query_stats – This existing DMV has new columns added that return very useful information. These new columns are listed as below:

  • total_rows – Returns the total number of rows returned by the query
  • last_rows – Returns the total number of rows returned by last execution of the query.
  • min_rows – Returns the minimum number of rows query returned over the number of times that the plan has executed since it was last compiled.
  • max_rows – Returns the maximum number of rows query returned over the number of times that the plan has executed since it was last compiled.

Usage:

USE [master]
GO

SELECT * FROM sys.dm_exec_query_stats;
GO

Example:

Permissions:

Requires VIEW SERVER STATE permission on the server.

MSDN reference: http://msdn.microsoft.com/en-us/library/ms189741.aspx

Conclusion

In this article, I've covered the new useful DMVs of SQL Server 2008 R2 SP1 and SQL Server 2012 (DENALI). These DMVs help us to manage our SQL Servers efficiently by returning some very useful information. It is difficult to retrieve similar kind of information in older versions of SQL Servers and one need to write lengthy bespoke code to retrieve the similar information returned by these DMVs. I've already written some SSRS queries by using these DMVs which details the useful information which our companies auditors needs to audit our our SQL Servers.

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