APPLOCK_MODE (Transact-SQL)

'database_principal'

Is the user, role, or application role that can be granted permissions to objects in the database. The caller of the function must be a member of database_principal, dbo, or the db_owner fixed database role in order to call the function successfully.

'resource_name'

Is a lock resource name specified by the client application. The application must ensure that the resource name is unique. The specified name is hashed internally into a value that can be stored in the SQL Server lock manager. resource_name is nvarchar(255) with no default. resource_name is binary compared, and is case-sensitive regardless of the collation settings of the current database.

'lock_owner'

Is the owner of the lock, which is the lock_owner value when the lock was requested. lock_owner is nvarchar(32), and the value can be either Transaction (the default) or Session.

nvarchar(32)

Returns the lock mode held by the lock owner on a particular application resource. Lock mode can be any one of these values:

*This lock mode is a combination of other lock modes and cannot be explicitly acquired by using sp_getapplock.

Nondeterministic

Nonindexable

Nonparallelizable

Two users (User A and User B) with separate sessions run the following sequence of Transact-SQL statements.

User A runs:

USE AdventureWorks2012;
GO
BEGIN TRAN;
DECLARE @result int;
EXEC @result=sp_getapplock
    @DbPrincipal='public',
    @Resource='Form1',
    @LockMode='Shared',
    @LockOwner='Transaction';
SELECT APPLOCK_MODE('public', 'Form1', 'Transaction');
GO

User B then runs:

Use AdventureWorks2012;
GO
BEGIN TRAN;
SELECT APPLOCK_MODE('public', 'Form1', 'Transaction');
--Result set: NoLock

SELECT APPLOCK_TEST('public', 'Form1', 'Shared', 'Transaction');
--Result set: 1 (Lock is grantable.)

SELECT APPLOCK_TEST('public', 'Form1', 'Exclusive', 'Transaction');
--Result set: 0 (Lock is not grantable.)
GO

User A then runs:

EXEC sp_releaseapplock @Resource='Form1', @DbPrincipal='public';
GO

User B then runs:

SELECT APPLOCK_TEST('public', 'Form1', 'Exclusive', 'Transaction');
--Result set: '1' (The lock is grantable.)
GO

User A and User B then run:

COMMIT TRAN;
GO

Reference