Understanding Sch-M Locks...

Hi Guys,
I have written quite a big stored procedure which creates a temporary table (multi-session) and updates it. All the statements are encapsulated in a single transaction which is explicitly declared in the code. What happens is that a lock is being put by the server on that table (of type Sch-M) in order thus preventing any type of operations on it (including simple select)

Now, I want to be able read that table from within another transaction. Why is that I cannot use a table hint NOLOCK in the select statement?

Here is some code which reproduces my problem.

Query A:



SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;

BEGIN TRAN TR_DEMO;

CREATE TABLE ##TBL1(
Oidx int not null primary key identity(1,1),
Name nvarchar(30) not null,
Type char(1) not null
);


INSERT ##TBL1 (Name,Type) VALUES ('Car','M');

WAITFOR DELAY '00:00:10';

INSERT ##TBL1 (Name,Type) VALUES ('Plane','M');

WAITFOR DELAY '00:00:10';

INSERT ##TBL1 (Name,Type) VALUES('Submarine','M');

WAITFOR DELAY '00:00:10';

DELETE FROM ##TBL1;

DROP TABLE ##TBL1;

COMMIT TRAN TR_DEMO;



Query B:

SELECT TOP 1 * FROM ##TBL1 (NOLOCK) ORDER BY oidx DESC;

Launch query A and then execute query B.

Thanks a lot for your help.