API approach to find On Hand Quantity of an Item

Below script is useful in finding On hand quantity accurately using Oracle Standard API INV_QUANTITY_TREE_PUB.QUERY_QUANTITIES. This script is tested in R12.1.3 instance.

DECLARE
   x_return_status         VARCHAR2 (50);
   x_msg_count             VARCHAR2 (50);
   x_msg_data              VARCHAR2 (50);
   v_item_id               NUMBER;
   v_org_id                NUMBER;
   v_qoh                   NUMBER;
   v_rqoh                  NUMBER;
   v_atr                   NUMBER;
   v_att                   NUMBER;
   v_qr                    NUMBER;
   v_qs                    NUMBER;
   v_lot_control_code      BOOLEAN;
   v_serial_control_code   BOOLEAN;
BEGIN
   -- Set the variable values
   v_item_id := &item_id;
   v_org_id := &org_id;
   v_qoh := NULL;
   v_rqoh := NULL;
   v_atr := NULL;
   v_lot_control_code := FALSE;
   v_serial_control_code := FALSE;
   
   -- Set the org context
   fnd_client_info.set_org_context (1);
   
   -- Call API
   inv_quantity_tree_pub.query_quantities
               (p_api_version_number       => 1.0,
                p_init_msg_lst             => 'F',
                x_return_status            => x_return_status,
                x_msg_count                => x_msg_count,
                x_msg_data                 => x_msg_data,
                p_organization_id          => v_org_id,
                p_inventory_item_id        => v_item_id,
                p_tree_mode                => apps.inv_quantity_tree_pub.g_transaction_mode,
                -- or 3
                p_is_revision_control      => FALSE,
                p_is_lot_control           => v_lot_control_code,
                -- is_lot_control,
                p_is_serial_control        => v_serial_control_code,
                p_revision                 => NULL,             -- p_revision,
                p_lot_number               => NULL,           -- p_lot_number,
                p_lot_expiration_date      => SYSDATE,
                p_subinventory_code        => NULL,    -- p_subinventory_code,
                p_locator_id               => NULL,       -- p_locator_id,
             -- p_cost_group_id            => NULL,       -- cg_id,
                p_onhand_source            => 3,
                x_qoh                      => v_qoh,   -- Quantity on-hand
                x_rqoh                     => v_rqoh,  --reservable quantity on-hand
                x_qr                       => v_qr,
                x_qs                       => v_qs,
                x_att                      => v_att,  -- available to transact
                x_atr                      => v_atr    -- available to reserve
               );
			   
   DBMS_OUTPUT.put_line ('On-Hand Quantity: ' || v_qoh);
   DBMS_OUTPUT.put_line ('Available to reserve: ' || v_atr);
   DBMS_OUTPUT.put_line ('Quantity Reserved: ' || v_qr);
   DBMS_OUTPUT.put_line ('Quantity Suggested: ' || v_qs);
   DBMS_OUTPUT.put_line ('Available to Transact: ' || v_att);
   DBMS_OUTPUT.put_line ('Available to Reserve: ' || v_atr);
EXCEPTION
   WHEN OTHERS
   THEN
      DBMS_OUTPUT.put_line ('ERROR: ' || SQLERRM);
END;