Transact-SQL Syntax ConventionsThis function returns information as to whether or not a lock can be granted on a particular application resource, for a specified lock owner, without acquisition of the lock. As an application lock function, APPLOCK_TEST operates on the current database. The database is the scope of the application locks.
Transact-SQL Syntax Conventions
’ database_principal ’
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.
’ resource_name ’
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.
’ lock_mode ’
The lock mode to obtaine for a specific resource. lock_mode is nvarchar(32), with no default value. lock_mode can have any of these values: Shared, Update, IntentShared, IntentExclusive, Exclusive.
’ lock_owner ’
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. If default or Transaction is explicitly specified, APPLOCK_TEST must be executed from within a transaction.
smallint
0 if the lock cannot be granted to the specified owner, or 1 if the lock can be granted.
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:
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:
APPLOCK_MODE (Transact-SQL)
sp_getapplock (Transact-SQL)
sp_releaseapplock (Transact-SQL)