gc current block busy

Hi ,

I have two node Oracle RAC.Version is 11.2.0.2

When i do an online inquire transaction for higher load, I am observing 'gc current block busy' in AWR as one of the top events.GV$SESSION_WAIT
doesnt show anything as below.

Kindly let me know how to tune it.

AWR top events.

DB CPU		32		64.34
log file sync	5,972	9	2	18.36	Commit
gc current block busy	2,448	7	23	13.32	Cluster
gc current block 2-way	4,665	3	1	5.41	Cluster
gc current grant busy	2,446	1	0	2.20	Cluster

SQL> SELECT
  INST_ID,
  EVENT,
  P1 FILE_NUMBER,
  P2 BLOCK_NUMBER,
  WAIT_TIME
FROM
  GV$SESSION_WAIT
WHERE
  EVENT IN ('buffer busy global cr', 'global cache busy',