After Migrating to RAC using Data Guard ,database is running very slowly

After Migrating to RAC(GI 11.2.0.3.2 and DB 11.2.0.3.0) using Data Guard on linux64 2.6.32-100,database is running very slowly.

but when i shutdown node2(or node1),database is running so fast.

#-------------------------------------node1 and node2 are up-------------------------------------------

FileComment
----------------------
SQL ID: 1v5kk0z5r6ww4
Plan Hash: 546168164
select count(*)
from
AR.RA_CUSTOMER_TRX_ALL


call     count       cpu    elapsed       disk      query    current        rows
------- ------  -------- ---------- ---------- ---------- ----------  ----------
Parse        2      0.03       0.03          0          0          0           0
Execute      2      0.00       0.00          0          0          0           0
Fetch        4      7.94     441.92      92877     188114          0           2
------- ------  -------- ---------- ---------- ---------- ----------  ----------
total        8      7.97     441.95      92877     188114          0           2

Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: SYS

Rows     Row Source Operation