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SQL Server, Locks Object

The SQLServer:Locks object in Microsoft SQL Server provides information about SQL Server locks on individual resource types. Locks are held on SQL Server resources, such as rows read or modified during a transaction, to prevent concurrent use of resources by different transactions. For example, if an exclusive (X) lock is held on a row within a table by a transaction, no other transaction can modify that row until the lock is released. Minimizing locks increases concurrency, which can improve performance. Multiple instances of the Locks object can be monitored at the same time, with each instance representing a lock on a resource type.

This table describes the SQL Server Locks counters.

SQL Server Locks counters Description

Average Wait Time (ms)

Average amount of wait time (in milliseconds) for each lock request that resulted in a wait.

Lock Requests/sec

Number of new locks and lock conversions per second requested from the lock manager.

Lock Timeouts (timeout > 0)/sec

Number of lock requests per second that timed out, but excluding requests for NOWAIT locks.

Lock Timeouts/sec

Number of lock requests per second that timed out, including requests for NOWAIT locks.

Lock Wait Time (ms)

Total wait time (in milliseconds) for locks in the last second.

Lock Waits/sec

Number of lock requests per second that required the caller to wait.

Number of Deadlocks/sec

Number of lock requests per second that resulted in a deadlock.

SQL Server can lock these resources.

Item Description

_Total

Information for all locks.

AllocUnit

A lock on an allocation unit.

Application

A lock on an application-specified resource.

Database

A lock on a database, including all objects in the database.

Extent

A lock on a contiguous group of 8 pages.

File

A lock on a database file.

Heap/BTree

Heap or BTree (HOBT). A lock on a heap of data pages, or on the BTree structure of an index.

Key

A lock on a row in an index.

Metadata

A lock on a piece of catalog information, also called metadata.

Object

A lock on table, stored procedure, view, etc, including all data and indexes. The object can be anything that has an entry in sys.all_objects.

Page

A lock on an 8-kilobyte (KB) page in a database.

RID

Row ID. A lock on a single row in a heap.

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