Using a VIEW to UNION two tables yields an Out of Spool Space condition

Analytics

Using a VIEW to UNION two tables yields an Out of Spool Space condition

I created a view that unions all columns in two identical tables together. They are identical in structure but not data content. When I run the SQL and join fields against the view I run out of spool space. But when I create a SQL statement that unions the one table's data with the other table, the query runs just fine. Why does using the view cause us to run out of spool space. We have COLLECT STATISTICS on all the joined fields. Any thoughts?

Example View with UNION
REPLACE VIEW PRODVW.Sales_Credit_Trans_C AS
LOCKING PRODDB.Sales_Credit_Trans FOR ACCESS
LOCKING PRODDB.Sales_Credit_Trans_Hist FOR ACCESS
SELECT *
FROM PRODDB.Sales_Credit_Trans_Hist
union
SELECT *
FROM PRODDB.Sales_Credit_Trans;

SQL that is being run
SELECT
PRODVW.Legal_Hierarchy_C.Legal_Parent_Cd,
PRODVW.Legal_Hierarchy_C.Legal_Parent_Nm,
( PRODVW.Legal_Hierarchy_C.Legal_Parent_Cd ) || ( PRODVW.Legal_Hierarchy_C.Legal_Division_Cd ),
PRODVW.Legal_Hierarchy_C.Legal_Division_Nm,
--PRODVW.Fiscal_Calendar.Fiscal_Yr,
PRODVW.Sales_Sub_Office_Hierarchy_V2.Sales_Region_Cd,
PRODVW.Sales_Rep_Hierarchy_V2.Sales_Rep_Nb,
PRODVW.Sales_Rep_Hierarchy_V2.Sales_Rep_Nm,
sum(PRODVW.Sales_Credit_Trans_C.Dist_Sales_Credit_Sell_Am) ,
PRODVW.Sales_Credit_Trans_C.Rep_Split_Pc,
PRODVW.Customer_C.Customer_Nb,
PRODVW.Customer_C.Customer_Nm
FROM
PRODVW.Legal_Hierarchy_C,
-- PRODVW.Fiscal_Calendar,
PRODVW.Sales_Sub_Office_Hierarchy_V2,
PRODVW.Sales_Rep_Hierarchy_V2,
PRODVW.Sales_Credit_Trans_C LEFT JOIN PRODVW.Customer_C ON PRODVW.Sales_Credit_Trans_C.Trans_Bill_To_Customer_Id=PRODVW.Customer_C.Customer_Id
WHERE
( PRODVW.Legal_Hierarchy_C.Customer_Id=PRODVW.Customer_C.Customer_Id )
AND ( PRODVW.Sales_Credit_Trans_C.Rep_Sales_Rep_Id=PRODVW.Sales_Rep_Hierarchy_V2.Sales_Rep_Id )
AND ( PRODVW.Sales_Sub_Office_Hierarchy_V2.Sales_Sub_Office_Id=PRODVW.Sales_Credit_Trans_C.Rep_Sales_Sub_Office_Id )
AND PRODVW.Sales_Credit_Trans_C.Fiscal_Ym >= 201001
-- AND ( PRODVW.Fiscal_Calendar.Fiscal_Ym=PRODDB.Sales_Credit_Trans_Hist.Fiscal_Ym )
-- AND ( PRODVW.Fiscal_Calendar.Fiscal_Ym >= 201001
AND PRODVW.Legal_Hierarchy_C.Legal_Parent_Cd IN ('998787', '079452', '101314')
GROUP BY
1, 2, 3, 4, 5, 6, 7, 9, 10, 11