Too many active Scans (no replies)

Hi,
I am performance testing the ndb cluster 7.3.3 using sysbench.
when I try to test using 1000 threads,I got the following error:
"ALERT: MySQL error: Got temporary error 245 'Too many active scans' from NDBCLUSTER"
The sysbench script is "sysbench --test=oltp --mysql-user=xxx --mysql-password=xxx --mysql-host=xxx --oltp-table-size=500000 --mysql-db=test --max-requests=50000 --num-threads=1000 --mysql-table-engine=ndbcluster --oltp-read-only=on run".

I found this URL http://planet.mysql.com/entry/?id=34190
and change the configuration as follows：
MaxNoOfConcurrentScans=500
MaxNoOfLocalScans=200000

But it doesn't work. The error still appears.

Is anyone kown how to fix it?

Thanks.