title: Retaining Delta log transaction data of Delta Lake forever
body: <p>I had a small confusion on transactional log of Delta lake. In the documentation it is mentioned that by default retention policy is 30 days and can be modified by property -: <code>delta.logRetentionDuration=interval-string</code> .
  But I don't understand when the actual log files are deleted from the delta_log folder. Is it when we run some operation? Or may be VACCUM operation. However, it is mentioned that VACCUM operation only deletes data files and not logs. But will it delete logs older than specified log retention duration?</p>
  <p>reference -: <a href="https://docs.databricks.com/delta/delta-batch.html#data-retention" rel="nofollow noreferrer">https://docs.databricks.com/delta/delta-batch.html#data-retention</a></p>