title: Snapshot reliability
body: <p>I'm sure this question has been answered elsewhere, but I'm not sure how to ask it, so I'm not sure how to search for an answer.  I apologize in advance.</p>
  
  <p>We are using an accrual accounting method.  I don't understand accounting.  I'm told that for the current period the previous period is subtracted and the new period is added leaving a view of the current state of the company.</p>
  
  <p>I inherited a 'data warehouse' (I use the term loosely) that takes a snapshot of the operational data every week (the period).  The snapshot table has year, month, and period # set according to the date the ETL jobs run.  The key to the fact table is the date the job is run and not necessarily tied to facts in the records.  Everything works fine and Management is happy.</p>
  
  <p>My concern is what happens if there is a system outage and the jobs do not run as scheduled?  As the operational data is constantly changing, if the ETL jobs don't run the same date and time each week, that week's snapshot will be corrupt, at least as compared to other weeks that did run on time.</p>
  
  <p>Is this a common problem?  Is it a bad design?  </p>