This message indicates that the query performs a table scan. The following query shows a typical table scan:
select au_lname, au_fname from authors
QUERY PLAN FOR STATEMENT 1 (at line 1). STEP 1 The type of query is SELECT. FROM TABLE authors Nested iteration. Table Scan. Forward scan. Positioning at start of table. Using I/O Size 16 Kbytes for data pages. With LRU Buffer Replacement Strategy for data pages.