title: What would cause SQL one or multiple databases to switch to single-user mode?
body: <p>Have over 25 databases throughout our organization. Over the weekend 7 of them automatically switched to single-user mode. We have no idea why. We were able to switch them back, but were confused as to why they jumped from multi-user mode randomly. </p>
  
  <p>There may be 2 catalysts: 
  1. Hard drive ran out of free space. Backups and transaction logs being backed up to same drive, caused it to run out of free space. </p>
  
  <ol>
  <li>Ran Shrink Database script on 3 of those 7 databases hours before the incidents. </li>
  </ol>
  
  <p>Have checked event logs, but only errors it shows for that day is the "out of space" issue. </p>
  
  <p>Any input would be appreciated. </p>