These are the Views which gives current state of the SQL Server Machine. There are two types of DMV's
a. sys.dm_os_sys_info
This view returns the information about the SQL Server machine, available resources and the resource consumption.
This view returns information like the following:
- CPU Count: Number of logical CPUs in the server
- Hyperthread-ratio: Ratio of logical and physical CPUs
Physical_memory_in_bytes: Amount of physical memory availableVirtual_memory_in_bytes: Amount of virtual memory availableBpool_commited: Committed physical memory in buffer poolOS_Priority_class: Priority class for SQL Server processMax_workers_thread: Maximum number of workers which can be created
b. sys.dm_os_hosts
This view returns all the hosts registered with SQL Server 2005. This view also provides the resources used by each host.
Name: Name of the host registered Type: Type of hosted component [SQL Native Interface/OLE DB/MSDART] Active_tasks_count: Number active tasks host placed Active_ios_count: I/O requests from host waiting
c. sys.dm_os_schedulers
Sys.dm_os_schedulers view will help you identify if there is any CPU bottleneck in the SQL Server machine. The number of runnable tasks is generally a nonzero value; a nonzero value indicates that tasks have to wait for their time slice to run. If the runnable task counts show high values, then there is a symptom of CPU bottleneck.
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Copy CodeSELECT
scheduler_id,current_tasks_count,runnable_tasks_count
FROM sys.dm_os_schedulers
WHERE scheduler_id < 255
The above query will list all the available schedulers in the SQL Server machine and the number of runnable tasks for each scheduler.
d. sys.dm_io_pending_io_requests
This dynamic view will return the I/O requests pending in SQL Server side. It gives you information like:
Io_type: Type of pending I/O requestIo_pending: Indicates whether the I/O request is pending or has been completed by WindowsScheduler_address: Scheduler on which this I/O request was issued
e. sys.dm_io_virtual_file_stats
This view returns I/O statistics for data and log files [MDF and LDF file]. This view is one of the commonly used views and will help you to identify I/O file level. This will return information like:
Sample_ms: Number of milliseconds since the instance of SQL Server has startedNum_of_reads: Number of reads issued on the fileNum_of_bytes_read: Total number of bytes read on this fileIo_stall_read_ms: Total time, in milliseconds, that the users waited for reads issued on the fileNum_of_writes: Number of writes made on this fileNum_of_bytes_written: Total number of bytes written to the fileIo_stall_write_ms: Total time, in milliseconds, that users waited for writes to be completed on the fileIo_stall: Total time, in milliseconds, that users waited for I/O to be completedSize_on_disk_bytes: Number of bytes used on the disk for this file
f. sys.dm_os_memory_clerks
This
DMV will help how much memory SQL Server has allocated through AWE.
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Copy Code SELECT
SUM(awe_allocated_kb) / 1024 as [AWE allocated, Mb]
FROM sys.dm_os_memory_clerks
The same
DMV can be used to get the memory consumption by internal components of SQL Server 2005.
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Copy Code SELECT TOP 10 type,
SUM(single_pages_kb) as [SPA Mem, Kb]
FROM sys.dm_os_memory_clerks
GROUP BY type
ORDER BY SUM(single_pages_kb) DESC
g. sys.dm_os_ring_buffers
This
DMV uses
RING_BUFFER_RESOURCE_MONITOR and gives information from resource monitor notifications to identify memory state changes. Internally, SQL Server has a framework that monitors different memory pressures. When the memory state changes, the resource monitor task generates a notification. This notification is used internally by the components to adjust their memory usage according to the memory state.
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Copy Code SELECT
Record FROM sys.dm_os_ring_buffers
WHERE ring_buffer_type = 'RING_BUFFER_RESOURCE_MONITOR'
The output of the above query will be in XML format. The output will help you in detecting any low memory notification.
RING_BUFFER_OOM: Ring buffer oom contains records indicating server out-of-memory conditions.
Frequently Used DMV's - DB SCOPE
a. sys.dm_db_file_space_usage
This
DMV provides the space usage information of
TEMPDB database.
b. sys.dm_db_session_space_usage
This
DMV provides the number of pages allocated and de-allocated by each session for the database
c. sys.dm_db_partition_stats
This
DMV provides page and row-count information for every partition in the current database.
The below query shows all counts for all partitions of all indexes and heaps in the MSDB database:
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Copy Code USE MSDB;
GO
SELECT * FROM sys.dm_db_partition_stats;
The following query shows all counts for all partitions of Backup set table and its indexes
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Copy Code USE MSDB
GO
SELECT * FROM sys.dm_db_partition_stats
WHERE object_id = OBJECT_ID('backupset');d. sys.dm_os_performance_counters
Returns the SQL Server / Database related counters maintained by the server.
The below sample query uses the
dm_os_performance_counters DMV to get the Log file usage for all databases in KB.
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Copy Code SELECT instance_name
,cntr_value 'Log File(s) Used Size (KB)'
FROM sys.dm_os_performance_counters
WHERE counter_name = 'Log File(s) Used Size (KB)'
3. INDEX Related DMV
This section details the
DMVs associated with SQL Server Databases. These
DMVs will help to identify database space usages, Partition usages, Session information usages, etc.
a. sys.dm_db_index_usage_stats
This
DMV is used to get useful information about the index usage for all objects in all databases. This also shows the amount of seeks and scan for each index.
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Copy Code SELECT object_id, index_id, user_seeks, user_scans, user_lookups
FROM sys.dm_db_index_usage_stats
ORDER BY object_id, index_id
All indexes which have not been used so far in as database can be identified using the below Query:
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Copy Code SELECT object_name(i.object_id),
i.name,
s.user_updates,
s.user_seeks,
s.user_scans,
s.user_lookups
from sys.indexes i
left join sys.dm_db_index_usage_stats s
on s.object_id = i.object_id and
i.index_id = s.index_id and s.database_id = 5
where objectproperty(i.object_id, 'IsIndexable') = 1 and
s.index_id is null or
(s.user_updates > 0 and s.user_seeks = 0
and s.user_scans = 0 and s.user_lookups = 0)
order by object_name(i.object_id)
Replace the
Database_id with the database you are looking at.
4. Execution Related DMV
Execution related
DMVs will provide information regarding sessions, connections, and various requests which are coming into the SQL Server.
a. sys.dm_exec_sessions
This
DMV will give information on each session connected to SQL Server. This
DMV is similar to running
sp_who2 or querying Master..
sysprocesses table.
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Copy Code SELECT
session_id,login_name,
last_request_end_time,cpu_time
FROM sys.dm_exec_sessions
WHERE session_id >= 51 – All user Sessions
b. sys.dm_exec_connections
This
DMV shows all the connection to SQL Server. The below query uses
sys.dm_exec_connections DMV to get connection information. This view returns one row for each user connection (
Sessionid > =51).
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Copy Code SELECT
connection_id,
session_id,client_net_address,
auth_scheme
FROM sys.dm_exec_connections
c. sys.dm_exec_requests
This
DMV will give details on what each connection is actually performing in SQL Server.
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Copy Code SELECT
session_id,status,
command,sql_handle,database_id
FROM sys.dm_exec_requests
WHERE session_id >= 51
d. sys.dm_exec_sql_text
This dynamic management function returns the text of a SQL statement given a SQL handle.
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Copy Code SELECT
st.text
FROM
sys.dm_exec_requests r
CROSS APPLY
sys.dm_exec_sql_text(sql_handle) AS st
WHERE r.session_id = 51
Execute Permissions For User
- GRANT VIEW SERVER STATE to
- GRANT VIEW DATABASE STATE to