Simple sql using distinct and union too slow

[gmerabella]

Here is a query
select distinct fiscal_year, accounting_period
from ps_ledger
union
select distinct fiscal_year, accounting_period
from ps_ledger_kk
union
select distinct fiscal_year, accounting_period
from ps_ledger_budg

The tables have about 1 million rows each.

Here is the explain plan

Operation Object Name Rows Bytes Cost Object Node In/Out PStart PStop

SELECT STATEMENT Optimizer Mode=ALL_ROWS 32 27811
SORT UNIQUE 32 253 27811
UNION-ALL
INDEX FAST FULL SCAN SYSADM.PSFLEDGER 1 M 11 M 5598
INDEX FAST FULL SCAN SYSADM.PSALEDGER_KK 948 K 7 M 7389
INDEX FAST FULL SCAN SYSADM.PS_LEDGER_BUDG 363 K 2 M 3064

It takes about 5 secs. I want it to run in 1 sec or less. Any ideas?