Issue regarding SQL Tuning

Hi

SQL : 1
Following Hierarchical SQL giving output with 2 seconds with 1169 records.

SELECT LPAD ('.', 2 * (LEVEL - 1), '.') || LEVEL bom_level,
msia.segment1
|| '.'
|| msia.segment2
|| '.'
|| msia.segment3
|| '.'
|| msia.segment4 parent_item_code,
msia.description parent_description, msia.primary_unit_of_measure,
LPAD ('.', 2 * (LEVEL - 1), '.')
|| msic.segment1
|| '.'
|| msic.segment2
|| '.'
|| msic.segment3
|| '.'
|| msic.segment4 component_item_code,
msic.description component_description, bic.operation_seq_num,
bic.component_quantity
FROM bom_bill_of_materials bom,
bom_inventory_components bic,
mtl_system_items msia,
mtl_system_items msic