Optimaze SQL Database table for multiple writes single read - sql-server

Question

I am developing a feature that will be used as processes progress monitor.
I will span 40-50 threads that might take several minutes or even hours to finish and they will update it's status to a datatable.
From the web app i will create a polling mechanism that will read the processes status using one read every 0.5 sec.
I need to optimize the table for multiple writes at a sec and one read per 0.5 sec. I don't care if I read a dirty state since it's just for monitoring the process, it's not that critical.
This is the table I am using
CREATE TABLE [cmn].[ProcessProgress]
(
[id] [bigint] NOT NULL,
[status] [smallint] NOT NULL,
[step] [int] NOT NULL,
[max_step] [int] NOT NULL,
CONSTRAINT [PK_ProcessProgress] PRIMARY KEY CLUSTERED
(
[id] ASC
) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
)
GO
And the select with (NOLOCK) I suppose I have to use
SELECT * FROM [cmn].[ProcessProgress] (NOLOCK)
Do I have to use a transaction with a special ISOLATION LEVEL or (nolock) is sufficient? Or (nolock) will make thinks worse?
Can you suggest what would be the most optimized solution for this problem?

Answer 1

Just set the READ_COMMITTED_SNAPSHOT option on your database, and the readers and writers will never conflict. Instead they will use Row Versioning:
alter database current set read_committed_snapshot on
In addition to increasing the concurrency and scalability of your application by eliminating blocking between readers and writers, it eliminates many deadlocks, and removes the incentive to perform dirty reads.

Answer 2

Here is an example (hope id did not make too many mistakes). test code at the bottom is what would be executed by each thread.
if object_id('ProcessProgress') is not null
drop table ProcessProgress
Go
CREATE TABLE [ProcessProgress]
(
[id] [bigint] NOT NULL IDENTITY(1,1), --added identity to shorten sample dev
[status] [smallint] NOT NULL, --1 -ready,2-inprogress, 3-complete
[step] [int] NOT NULL,
[max_step] [int] NOT NULL,
CONSTRAINT [PK_ProcessProgress] PRIMARY KEY CLUSTERED
(
[id] ASC
) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
)
GO
SET NOCOUNT ON
INSERT INTO [ProcessProgress]
(status, step, max_step)
VALUES
(1, 1, 1)
GO 1000
Go
IF OBJECT_ID('StartWork') is not null drop proc StartWork
GO
CREATE PROC StartWork
AS
BEGIN
SET TRANSACTION ISOLATION LEVEL READ COMMITTED
BEGIN TRAN
;WITH TODO
AS (
SELECT TOP 1 Id, [status] from ProcessProgress WITH (ROWLOCK, READPAST) WHERE [status] = 1 --ready
)
UPDATE TODO
SET [status] = 2 --InProgress
OUTPUT inserted.id
COMMIT
END
GO
IF OBJECT_ID('FinishWork') is not null drop proc FinishWork
GO
CREATE PROC FinishWork
#id int
AS
BEGIN
SET TRANSACTION ISOLATION LEVEL READ COMMITTED
BEGIN TRAN
Update ProcessProgress
SET [Status] = 3 --finished
WHERE
id = #id
COMMIT
END
GO
/*tester*/
declare #idout table (id int)
insert into #idout exec StartWork
declare #idin int = (Select top 1 id from #idout)
exec FinishWork #idin