Using the Compiler's xref To learn what index or indexes the compiler will use, compile with the xref option. No bracketing also means that the entire index is bracketed. This will result in a full index scan, reading every index entry, to retrieve the rows. This indicates that two indexes Name and Sales-Rep are being used. In this case index Cust-num and Name are used.
Name appears twice indicating two separate brackets on name are used.
This is because index entries will be added or deleted when rows are added or deleted. The more indexes you have, the more index entries will have to be added or deleted. Slower updates of index columns. This is because the index entries must be updated whenever a column that is a component of an index is updated with a new value. Additional storage space.