The short answer is you can ignore these. When you are using Hive Streaming Ingest (https://cwiki.apache.org/confluence/display/Hive/Streaming+Data+Ingest) which is used by Storm/Flume/NiFi, Hive creates these file for it's internal housekeeping for maintaining transactional consistency. They should normally be removed as soon as the TransactionBatch is closed (usually once transaction Y of delta_X_Y/ finishes). The flush_legth file may remain around if the Writer process crashes before TransactionBatch is closed. They will eventually be cleaned by the Compactor process. ... View more