SQL4012 - Index created from index &1 for table &2

SQL4012
Message Text: Index created from index &1 for table &2
Cause Text: A temporary index was created using the specified index to access rows from the queried table for one of the following reasons:
  • Perform specified ordering/grouping criteria.
  • Perform specified join criteria.
The table number refers to the relative position of this table in the query.
Recovery Text: Creating an index from an index is generally a good performing option. Consider creating a permanent index for frequently run queries. The query can be run in debug mode (STRDBG) to determine the key columns used when creating the index. NOTE: If a permanent index is created, it is possible the query optimizer may still choose to create a temporary index to access the rows from the table.