ALTER TABLE ... MERGE PARTITION
statement to merge the contents of two partitions into one partition. The two original partitions are dropped, as are any corresponding local indexes.
You cannot use this statement for a hash-partitioned table or for hash subpartitions of a composite *-hash partitioned table.
You cannot merge partitions for a reference-partitioned table. Instead, a merge operation on a parent table will cascade to all descendant tables. However, you can use the DEPENDENT TABLES clause to set specific properties for dependent tables when you issue the merge operation on the master table to merge partitions or subpartitions