SQL query

I have a SQL query that reads data from mainframe tables. It runs very slow even the it returns 10 records.
Could anyone hlep to improve the performance?

SELECT DISTINCT
T1.COL_ID as ID, T2.COL_SHORT_NAME AS ShortName,T2.COL_NAME AS Name
FROM TABLE1 T1, TABLE2 T2
WHERE T1.COL_ID = T2.COL_ID
AND (T1.BEG_DT <= '20080410') AND (T1.RATE_END_DT >= '20080410')
UNION
SELECT COL_ID AS ID, SUBSTR(COL_PLAN_NAME, 1, 3) AS ShortName, COL_PLAN_NAME AS Name
FROM TABLE3
ORDER BY ShortName

Do you have index on COL_ID, T1.BEG_DT or T1.RATE_END_DT