sys.dm_tran_locks (Transact-SQL)
Returns information about currently active lock manager resources. Each row represents a currently active request to the lock manager for a lock that has been granted or is waiting to be granted.
The columns in the result set are divided into two main groups: resource and request. The resource group describes the resource on which the lock request is being made, and the request group describes the lock request.
Column name |
Data type |
Description |
|---|---|---|
resource_type |
nvarchar(60) |
Represents the resource type. The value can be one of the following: DATABASE, FILE, OBJECT, PAGE, KEY, EXTENT, RID, APPLICATION, METADATA, HOBT, or ALLOCATION_UNIT. |
resource_subtype |
nvarchar(60) |
Represents a subtype of resource_type. Acquiring a subtype lock without holding a nonsubtyped lock of the parent type is technically valid. Different subtypes do not conflict with each other or with the nonsubtyped parent type. Not all resource types have subtypes. |
resource_database_id |
int |
ID of the database under which this resource is scoped. All resources handled by the lock manager are scoped by the database ID. |
resource_description |
nvarchar(256) |
Description of the resource that contains only information that is not available from other resource columns. |
resource_associated_entity_id |
bigint |
ID of the entity in a database with which a resource is associated. This can be an object ID, Hobt ID, or an Allocation Unit ID, depending on the resource type. |
resource_lock_partition |
Int |
ID of the lock partition for a partitioned lock resource. The value for nonpartitioned lock resources is 0. |
request_mode |
nvarchar(60) |
Mode of the request. For granted requests, this is the granted mode; for waiting requests, this is the mode being requested. |
request_type |
nvarchar(60) |
Request type. The value is LOCK. |
request_status |
nvarchar(60) |
Current status of this request. Possible values are GRANTED, CONVERT, or WAIT. |
request_reference_count |
smallint |
Returns an approximate number of times the same requestor has requested this resource. |
request_lifetime |
int |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
request_session_id |
int |
Session ID that currently owns this request. The owning session ID can change for distributed and bound transactions. A value of -2 indicates that the request belongs to an orphaned distributed transaction. A value of -3 indicates that the request belongs to a deferred recovery transaction, such as, a transaction for which a rollback has been deferred at recovery because the rollback could not be completed successfully. |
request_exec_context_id |
int |
Execution context ID of the process that currently owns this request. |
request_request_id |
int |
Request ID (batch ID) of the process that currently owns this request. This value will change every time that the active Multiple Active Result Set (MARS) connection for a transaction changes. |
request_owner_type |
nvarchar(60) |
Entity type that owns the request. Lock manager requests can be owned by a variety of entities. Possible values are: TRANSACTION = The request is owned by a transaction. CURSOR = The request is owned by a cursor. SESSION = The request is owned by a user session. SHARED_TRANSACTION_WORKSPACE = The request is owned by the shared part of the transaction workspace. EXCLUSIVE_TRANSACTION_WORKSPACE = The request is owned by the exclusive part of the transaction workspace. .gif "Note") Note
Work spaces are used internally to hold locks for enlisted sessions.
|
request_owner_id |
bigint |
ID of the specific owner of this request. This value is only used for transactions for which this is the transaction ID. |
request_owner_guid |
uniqueidentifier |
GUID of the specific owner of this request. This value is only used by a distributed transaction where the value corresponds to the MS DTC GUID for that transaction. |
request_owner_lockspace_id |
nvarchar(32) |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. This value represents the lockspace ID of the requestor. The lockspace ID determines whether two requestors are compatible with each other and can be granted locks in modes that would otherwise conflict with one another. |
lock_owner_address |
varbinary(8) |
Memory address of the internal data structure that is used to track this request. This column can be joined the with resource_address column in sys.dm_os_waiting_tasks. |
Permissions
Requires VIEW SERVER STATE permission on the server.
Remarks
A granted request status indicates that a lock has been granted on a resource to the requestor. A waiting request indicates that the request has not yet been granted. The following waiting-request types are returned by the request_status column:
A convert request status indicates that the requestor has already been granted a request for the resource and is currently waiting for an upgrade to the initial request to be granted.
A wait request status indicates that the requestor does not currently hold a granted request on the resource.
Because sys.dm_tran_locks is populated from internal lock manager data structures, maintaining this information does not add extra overhead to regular processing. Materializing the view does require access to the lock manager internal data structures. This can have minor effects on the regular processing in the server. These effects should be unnoticeable and should only affect heavily used resources. Because the data in this view corresponds to live lock manager state, the data can change at any time, and rows are added and removed as locks are acquired and released. This view has no historical information.
Two requests operate on the same resource only if all the resource-group columns are equal.
You can control the locking of read operations by using the following tools:
SET TRANSACTION ISOLATION LEVEL to specify the level of locking for a session. For more information, see SET TRANSACTION ISOLATION LEVEL (Transact-SQL).
Locking table hints to specify the level of locking for an individual reference of a table in a FROM clause. For syntax and restrictions, see Table Hints (Transact-SQL).
A resource that is running under one session ID can have more than one granted lock. Different entities that are running under one session can each own a lock on the same resource, and the information is displayed in the request_owner_type and request_owner_id columns that are returned by sys.dm_tran_locks. If multiple instances of the same request_owner_type exist, the request_owner_id column is used to distinguish each instance. For distributed transactions, the request_owner_type and the request_owner_guid columns will show the different entity information.
For example, Session S1 owns a shared lock on Table1; and transaction T1, which is running under session S1, also owns a shared lock on Table1. In this case, the resource_description column that is returned by sys.dm_tran_locks will show two instances of the same resource. The request_owner_type column will show one instance as a session and the other as a transaction. Also, the resource_owner_id column will have different values.
Note
Multiple cursors that run under one session are indistinguishable and are treated as one entity.
For more information about the types of locks used by the SQL Server Database Engine, see Locking in the Database Engine.
Distributed transactions that are not associated with a session ID value are orphaned transactions and are assigned the session ID value of -2. For more information, see KILL (Transact-SQL).
Resource Details
The following table lists the resources that are represented in the resource_associated_entity_id column.
Resource type |
Resource description |
Resource_associated_entity_id |
|---|---|---|
DATABASE |
Represents a database. |
Not applicable |
FILE |
Represents a database file. This file can be either a data or a log file. |
Not applicable |
OBJECT |
Represents a database object. This object can be a data table, view, stored procedure, extended stored procedure, or any object that has an object ID. |
Object ID |
PAGE |
Represents a single page in a data file. |
HoBt ID. This value corresponds to sys.partitions.hobt_id. The HoBt ID is not always available for PAGE resources because the HoBt ID is extra information that can be provided by the caller, and not all callers can provide this information. |
KEY |
Represents a row in an index. |
HoBt ID. This value corresponds to sys.partitions.hobt_id. |
EXTENT |
Represents a data file extent. An extent is a group of eight contiguous pages. |
Not applicable |
RID |
Represents a physical row in a heap. |
HoBt ID. This value corresponds to sys.partitions.hobt_id. The HoBt ID is not always available for RID resources because the HoBt ID is extra information that can be provided by the caller, and not all callers can provide this information. |
APPLICATION |
Represents an application specified resource. |
Not applicable |
METADATA |
Represents metadata information. |
Not applicable |
HOBT |
Represents a heap or a B-tree. These are the basic access path structures. |
HoBt ID. This value corresponds to sys.partitions.hobt_id. |
ALLOCATION_UNIT |
Represents a set of related pages, such as an index partition. Each allocation unit covers a single Index Allocation Map (IAM) chain. |
Allocation Unit ID. This value corresponds to sys.allocation_units.allocation_unit_id. |
The following table lists the subtypes that are associated with each resource type.
ResourceSubType |
Synchronizes |
|---|---|
DATABASE.BULKOP_BACKUP_DB |
Database backups with bulk operations. |
DATABASE.BULKOP_BACKUP_LOG |
Database log backups with bulk operations. |
DATABASE.DDL |
Data definition language (DDL) operations with file group operations, such as drop. |
DATABASE.STARTUP |
Used for database startup synchronization. |
TABLE.UPDSTATS |
Statistics updates on a table. |
TABLE.COMPILE |
Stored procedure compile. |
TABLE.INDEX_OPERATION |
Index operations. |
HOBT.INDEX_REORGANIZE |
Heap or index reorganization operations. |
HOBT.BULK_OPERATION |
Heap-optimized bulk load operations with concurrent scan, under these isolation levels: snapshot, read uncommitted, and read committed using row versioning. |
ALLOCATION_UNIT.PAGE_COUNT |
Allocation unit page count statistics during deferred drop operations. |
METADATA.INDEXSTATS |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.STATS |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.XML_COLLECTION |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.SEQUENCE |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.QNAME |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.ASSEMBLY_CLR_NAME |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.ASSEMBLY_TOKEN |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.ASSEMBLY |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.PARTITION_FUNCTION |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.DATA_SPACE |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.USER_TYPE |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.DB_PRINCIPAL_SID |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.DATABASE_PRINCIPAL |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.SCHEMA |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.XML_COMPONENT |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.SERVER |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.INSTANTIATED_TYPE_HASH |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.DB_MIRRORING_SESSION |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.ENDPOINT |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.SECURITY_CACHE |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.DB_MIRRORING_WITNESS |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.CREDENTIAL |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.SECURITY_DESCRIPTOR |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.SERVICE_BROKER_GUID |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.CONVERSTATION_ENDPOINT_RECV |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.DATABASE |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.CONVERSATION_GROUP |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.ENDPOINT_WEBMETHOD |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.ASSYMMETRIC_KEY |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.FULLTEXT_CATALOG |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.FULLTEXT_INDEX |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.SERVER_PRINCIPAL |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.ROUTE |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.MESSAGE |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.QNAME_HASH |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.SERVICE_MESSAGE_TYPE |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.CONVERSTATION_ENDPOINT_SEND |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.CERTIFICATE |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.SYMMETRIC_KEY |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.XML_INDEX_QNAME |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.SERVICE_CONTRACT |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.REMOTE_SERVICE_BINDING |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.SERVICE |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.METADATA_CACHE |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
The following table provides the format of the resource_description column for each resource type.
Resource |
Format |
Description |
|---|---|---|
DATABASE |
Not applicable |
Database ID is already available in the resource_database_id column. |
FILE |
<file_id> |
ID of the file that is represented by this resource. |
OBJECT |
<object_id> |
ID of the object that is represented by this resource. This object can be any object listed in sys.objects, not just a table. |
PAGE |
<file_id>:<page_in_file> |
Represents the file and page ID of the page that is represented by this resource. |
KEY |
<hash_value> |
Represents a hash of the key columns from the row that is represented by this resource. |
EXTENT |
<file_id>:<page_in_files> |
Represents the file and page ID of the extent that is represented by this resource. The extent ID is the same as the page ID of the first page in the extent. |
RID |
<file_id>:<page_in_file>:<row_on_page> |
Represents the page ID and row ID of the row that is represented by this resource. Note that if the associated object ID is 99, this resource represents one of the eight mixed page slots on the first IAM page of an IAM chain. |
APPLICATION |
<DbPrincipalId>:<upto 32 characters>:(<hash_value>) |
Represents the ID of the database principal that is used for scoping this application lock resource. Also included are up to 32 characters from the resource string that corresponds to this application lock resource. In certain cases, only 2 characters can be displayed due to the full string no longer being available. This behavior occurs only at database recovery time for application locks that are reacquired as part of the recovery process. The hash value represents a hash of the full resource string that corresponds to this application lock resource. |
HOBT |
Not applicable |
HoBt ID is included as the resource_associated_entity_id. |
ALLOCATION_UNIT |
Not applicable |
Allocation Unit ID is included as the resource_associated_entity_id. |
METADATA.SEQUENCE |
$seq_type = S, object_id = O |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.STATS |
object_id = O, stats_id = S |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.SCHEMA |
schema_id = S |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.INDEXSTATS |
object_id = O, index_id or stats_id = I |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.DATABASE_PRINCIPAL |
principal_id = P |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.DB_PRINCIPAL_SID |
$hash = H1:H2:H3 |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.USER_TYPE |
user_type_id = U |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.DATA_SPACE |
data_space_id = D |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.PARTITION_FUNCTION |
function_id = F |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.PARTITION_FUNCTION |
function_id = F |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.ASSEMBLY |
assembly_id = A |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.ASSEMBLY_TOKEN |
assembly_id = A, $token_id = T |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.ASSEMBLY_CLR_NAME |
$qname_id = Q |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.QNAME |
$qname_id = Q |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.XML_COLLECTION |
xml_collection_id = X |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.XML_COMPONENT |
xml_component_id = X |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.QNAME_HASH |
$qname_scope_id = Q, $qname_hash = H |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.XML_INDEX_QNAME |
object_id = O, $qname_id = Q |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.SERVICE_MESSAGE_TYPE |
message_type_id = M |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.SERVICE_CONTRACT |
service_contract_id = S |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.SERVICE |
service_id = S |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.REMOTE_SERVICE_BINDING |
remote_service_binding_id = R |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.ROUTE |
route_id = R |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.FULLTEXT_INDEX |
object_id = O |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.FULLTEXT_CATALOG |
fulltext_catalog_id = F |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.CONVERSATION_GROUP |
conversation_group_id = C |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.CONVERSTATION_ENDPOINT_SEND |
$hash = H1:H2:H3 |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.CONVERSTATION_ENDPOINT_RECV |
$hash = H1:H2:H3 |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.SYMMETRIC_KEY |
symmetric_key_id = S |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.CERTIFICATE |
certificate_id = C |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.ASSYMMETRIC_KEY |
asymmetric_key_id = A |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.DATABASE |
database_id = D |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.MESSAGE |
message_id = M |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.SERVER_PRINCIPAL |
principal_id = P |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.SERVER |
server_id = S |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.ENDPOINT |
endpoint_id = E |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.ENDPOINT_WEBMETHOD |
$hash = H1:H2:H3 |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.DB_MIRRORING_SESSION |
database_id = D |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.DB_MIRRORING_WITNESS |
$hash = H1:H2:H3 |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.SERVICE_BROKER_GUID |
$hash = H1:H2:H3 |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.SERVICE_BROKER_GUID |
$hash = H1:H2:H3 |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.CREDENTIAL |
credential_id = C |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.INSTANTIATED_TYPE_HASH |
user_type_id = U, hash = H1 |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.SECURITY_DESCRIPTOR |
sd_id = S |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.SECURITY_CACHE |
$hash = H1:H2:H3 |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
METADATA.METADATA_CACHE |
$hash = H1:H2:H3 |
Identified for informational purposes only. Not supported. Future compatibility is not guaranteed. |
Examples
A. Using sys.dm_tran_locks with other tools
The following example works with a scenario in which an update operation is blocked by another transaction. By using sys.dm_tran_locks and other tools, information about locking resources is provided.
USE tempdb;
GO
-- Create test table and index.
CREATE TABLE t_lock
(
c1 int, c2 int
);
GO
CREATE INDEX t_lock_ci on t_lock(c1);
GO
-- Insert values into test table
INSERT INTO t_lock VALUES (1, 1);
INSERT INTO t_lock VALUES (2,2);
INSERT INTO t_lock VALUES (3,3);
INSERT INTO t_lock VALUES (4,4);
INSERT INTO t_lock VALUES (5,5);
INSERT INTO t_lock VALUES (6,6);
GO
-- Session 1
SET TRANSACTION ISOLATION LEVEL READ COMMITTED;
BEGIN TRAN
SELECT c1
FROM t_lock
WITH(holdlock, rowlock);
-- Session 2
BEGIN TRAN
UPDATE t_lock SET c1 = 10
The following query will display lock information. The value for <dbid> should be replaced with the database_id from sys.databases.
SELECT resource_type, resource_associated_entity_id,
request_status, request_mode,request_session_id,
resource_description
FROM sys.dm_tran_locks
WHERE resource_database_id = <dbid>
The following query returns object information by using resource_associated_entity_id from the previous query. This query must be executed while you are connected to the database that contains the object.
SELECT object_name(object_id), *
FROM sys.partitions
WHERE hobt_id=<resource_associated_entity_id>
The following query will show blocking information.
SELECT
t1.resource_type,
t1.resource_database_id,
t1.resource_associated_entity_id,
t1.request_mode,
t1.request_session_id,
t2.blocking_session_id
FROM sys.dm_tran_locks as t1
INNER JOIN sys.dm_os_waiting_tasks as t2
ON t1.lock_owner_address = t2.resource_address;
Release the resources by rolling back the transactions.
-- Session 1
ROLLBACK;
GO
-- Session 2
ROLLBACK;
GO
B. Linking session information to operating system threads
The following example returns information that associates a session ID with a Windows thread ID. The performance of the thread can be monitored in the Windows Performance Monitor. This query does not return session IDs that are currently sleeping.
SELECT STasks.session_id, SThreads.os_thread_id
FROM sys.dm_os_tasks AS STasks
INNER JOIN sys.dm_os_threads AS SThreads
ON STasks.worker_address = SThreads.worker_address
WHERE STasks.session_id IS NOT NULL
ORDER BY STasks.session_id;
GO