Question

I have a scheduler (created with c#) running in multiple machines, accessed a single database. on the table there are list of job to do. like below:

ID  JobDetail Flag
1   ---       1
2   ---       0
3   ---       0

Flag: 
0: open, 1: inprogress, 2: completed

my question is what should i do to make sure that there will no scheduler execute the same job.

sorry this question should be very general, if there is a dupe please point me a link.

Answer 1

try something like this:

SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;
GO

DECLARE @CURR_JOBID int;

SELECT @CURR_JOBID=top 1 ID FROM JOB_TABLE WHERE Flag=0 and <other condtions>

BEGIN TRANSACTION

UPDATE JOB_TABLE set Flag=1 where ID=@CURR_JOBID 

COMMIT

SET TRANSACTION ISOLATION LEVEL READ COMMITED;
GO

Now Use @CURR_JOBID for further processing

Once the job is finished, update the Flag to 2