title: What is exactly mean by 'DisallowConcurrentExecution' in Quartz.net
body: <p>I have a Quartz.net Job with the following definition.</p>
  
  <pre><code>    [PersistJobDataAfterExecution]
      [DisallowConcurrentExecution]
      public class AdItemsJob : IJob, IInterruptableJob
      {
  
          public void Execute(IJobExecutionContext context)
          { 
           // Job execution logic,
  
          }
     }
  </code></pre>
  
  <p>As I have decorated the Job with <code>DisallowConcurrentExecution</code> attribute.<br>
  What I know about this attribute, we can't run multiple instances of same job at the same time. What is meant by multiple instances here.?<br>
  Does the two jobs of <code>AddItemsJob</code>  with different key are called same instances or different instances.?<br>
  Does two jobs with different key can execute at the same time.?</p>