APPLOCK_MODE (Transact-SQL)
Returns the lock mode held by the lock owner on a particular application resource. APPLOCK_MODE is an application lock function, and it operates on the current database. The scope of application locks is the database.
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Transact-SQL Syntax Conventions
Syntax
APPLOCK_MODE('database_principal','resource_name','lock_owner')
Arguments
- '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 Microsoft 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.
Return Types
nvarchar(32)
Return Value
Returns the lock mode held by the lock owner on a particular application resource. Lock mode can be any one of these values:
NoLock |
Update |
*SharedIntentExclusive |
IntentShared |
IntentExclusive |
*UpdateIntentExclusive |
Shared |
Exclusive |
|
*This lock mode is a combination of other lock modes and cannot be explicitly acquired using sp_getapplock.
Function Properties
Nondeterministic
Nonindexable
Nonparallelizable
Examples
Two users (User A and User B) with separate sessions run the following sequence of Transact-SQL statements.
User A runs:
USE AdventureWorks;
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 AdventureWorks;
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 both run:
COMMIT TRAN;
GO
See Also
Reference
APPLOCK_TEST (Transact-SQL)
sp_getapplock (Transact-SQL)
sp_releaseapplock (Transact-SQL)