How to check whether a Timer Job has run

I'm not at work so this is off the top of my head, but: If you get a reference to the Site, can you try to create a new SPSite with the SYSTEM-UserToken?

SPUserToken sut = thisSite.RootWeb.AllUsers["SHAREPOINT\SYSTEM"].UserToken;

using (SPSite syssite = new SPSite(thisSite.Url,sut)
{
    // Do what you have to do
}

Anoop,

The "sweep" type of timer job you're describing is a fairly common one, and I've written a number of them myself for different projects. In this type of timer job, you're processing a set of sites, webs, or lists to perform some sort of maintenance. It's typically easiest to process one site/web/list at a time, and the task being performed isn't the type that needs to be performed with maximum speed (that is, something that would require a concurrent/multi-threaded processing model to complete quickly).

In this type of scenario, I've generally built my timer jobs to use an SPJobLockType of "Job." As you noted, this ensures that only one instance of the timer job is running at any given time within the farm. This avoids collisions that would occur if multiple instances ran with an SPJobLockType of "None," and it also avoids the confusing (at least I find it confusing) mechanism of operation that is associated with an SPJobLockType of "ContentDatabase."

Here's a link to the timer job I wrote and posted out on CodePlex. It performs the same type of sweep (at a slightly higher-level) that you were describing: http://blobcachefarmflush.codeplex.com/SourceControl/changeset/view/53851#797787. An instance of the timer job is created in a FeatureReceiver with the following line of code:

BlobCacheFarmFlushTimerJob newJob = new BlobCacheFarmFlushTimerJob(jobName, housingWebApp, null, SPJobLockType.Job);

Based on my understanding of what you've written, I believe an SPJobLockType of "Job" would be appropriate. You want to ensure that only one instance of your job is running at a time (to prevent two or more instances of the same job from trying to process the same SPSite).

I hope that helps!