This function returns the lock mode held by the lock owner on a particular application resource. As an application lock function, APPLOCK_MODE operates on the current database. The database is the scope of the application locks.
APPLOCK_MODE( 'database_principal' , 'resource_name' , 'lock_owner' )
The user, role, or application role that can be granted permissions to objects in the database. To successfully call the function, the function caller must be a member of database_principal, dbo, or the db_owner fixed database role.
A lock resource name specified by the client application. The application must ensure a unique resource name. The specified name is hashed internally into a value that the SQL Server lock manager can internally store. resource_nameis nvarchar(255), with no default. resource_name is binary compared, and is case-sensitive regardless of the collation settings of the current database.
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.
Returns the lock mode held by the lock owner on a particular application resource. Lock mode can have any one of these values:
*This lock mode is a combination of other lock modes and sp_getapplock cannot explicitly acquire it.
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