The NameNode also uses a transaction log to persistently record every change that occurs in filesystem metadata (metadata store). This log is stored in the EditLog file on the NameNode’s local filesystem. Edit log is a transactional log of every filesystem metadata change since the image file was created.
The Name Node uses a transaction log called the Edit Log to persistently record every change that occurs to file system metadata. For example, creating a new file in HDFS causes the Name Node to insert a record into the Edit Log indicating this. Similarly, changing the replication factor of a file causes a new record to be inserted into the Edit Log. The Name Node uses a file in its local host OS file system to store the Edit Log.