We've following SQL command within our application.

SELECT trackerid,taskid,action,sendto, sendtofullname, recfrom, actiontime 
FROM [LO].[dbo].[TRACKER] WITH (NOLOCK) 
where [EVENTRECORDID] = ? and ACTION in (1,4,5,15,4000,4200) 
order by Actiontime

It went a while also it was extremely swift, but last days it grew to become extreme gradually. I transformed it to

SELECT trackerid,taskid,action,sendto, sendtofullname, recfrom, actiontime 
FROM [LO].[dbo].[TRACKER] 
where [EVENTRECORDID] = ? and ACTION in (1,4,5,15,4000,4200) 
order by Actiontime

And So I take away the section WITH (NOLOCK).

Also it grew to become fast again. It can make me sense at all and that i have no clue, why it's this behavior. I'm also worried it grew to become slow again. Could somebody explain it in my experience?

And DB server is MS SQL 2008

Thanks

I in comparison the execution plans, and they're exactly the same.

One factor found my thoughts. Every evening we execute index reorganization (and once per week index rebuild). But after index reorganization we didn't remember update statistics. Could it possess some connection?