Alternative to Identity column - sql-server-2008

Question

we have Orders table with an identity column (OrderID) but our order number is composed by OrderType (2 chars), OrderYear (2 chars) and OrderID (6 chars), totally 10 chars (i.e. XX12123456).
This counter has limitations: we can arrive to identity 999999 as OrderID . Next order will have ID composed by 7 chars. Obviously we cannot ave duplicates order ids.
So we have created a table prefilled with progressive OrderID and OrderYear (from 100000 to 999999, order year from 12 to 16, for instance): this stored procedure begins a transacation with SERIALIZABLE isolation level, take first order id not used, update it as used and commit the transaction.
Being our Orders table, i'm worried about deadlocks on executing order id calculation stored procedure or duplicated orderids.
I'll test this with a console application that create multiple concurrency threads and try to extract orderids simulating a production load.
Doubts are:
Exists another method to simulate an identity column safely?
May consider usage of triggers?
May consider differente isolation level?
Other ideas? :D
Thanks!
[EDIT]
After googling and reading a bunch of MSDN documentation, i've found many examples showing how managing errors and dealocks and approaching a type of automatic reply directly from SP, as follow:
CREATE PROCEDURE [dbo].[sp_Ordine_GetOrderID]
#AnnoOrdine AS NVARCHAR(2) = NULL OUTPUT,
#IdOrdine AS INT = NULL OUTPUT
AS
SET NOCOUNT ON
DECLARE #retry AS INT
SET #retry = 2
SET TRANSACTION ISOLATION LEVEL SERIALIZABLE
WHILE (#retry > 0)
BEGIN
BEGIN TRY
BEGIN TRANSACTION OrderID
SELECT TOP 1 #AnnoOrdine = AnnoOrdine, #IdOrdine = IdOrdine
FROM ORDINI_PROGRESSIVI --WITH (ROWLOCK)
WHERE Attivo = 1
--ORDER BY AnnoOrdine ASC, IDOrdine ASC
UPDATE ORDINI_PROGRESSIVI WITH (UPDLOCK)
SET Attivo = 0
WHERE AnnoOrdine = #AnnoOrdine AND IdOrdine = #IdOrdine
IF ISNULL(#IdOrdine, '') = '' OR ISNULL(#AnnoOrdine,'') = ''
BEGIN
RAISERROR('Deadlock', 1, 1205)
END
SET #retry = 0
COMMIT TRANSACTION OrderID
SELECT #AnnoOrdine AS AnnoOrdine, #IdOrdine AS IdOrdine
END TRY
BEGIN CATCH
IF (ERROR_NUMBER() = 1205)
SET #retry = #retry - 1;
ELSE
SET #retry = -1;
IF XACT_STATE() <> 0
ROLLBACK TRANSACTION;
END CATCH
END
This approach reduce deadlocks (absent at all) but sometimes i got EMPTY output parameter.
Tested with 30 contemporary threads (so, 30 customers processes that insert orders at the same moment)
Here a debug log with query duration, in milliseconds: http://nopaste.info/285f558758.html
Enough robust for production?

Answer 1

If you do discover that the current solution is creating problems, and it's possible that it won't, then an alternative would be to have a table for each id type you want to create with an identity column and a dummy field
ie:
ABtypeID (ABID int identity(1,1), dummy varchar(1))
You can then insert a record into this table and use the built in functions to retrieve an identity.
ie
insert ABTypeID (dummy) values (null)
select Scope_Identity()
You can delete from these tables as and when you like, and truncacte them at year end to reset the id counters.
You can even wrap the insert in a transaction that gets rolled back - the identity value is not affected by the rollback