[Building Sakai] Problem with clustering??

[Omer A Piperdi]

Hi,

We are seeing app. server disappearing from sakai_cluster table, which 
leads to closing the session like below from server which is still in pool.

2012-09-12 15:56:29,113  INFO SakaiClusterService.Maintenance 
org.sakaiproject.cluster.impl.SakaiClusterService - Closed 2 orphaned 
usage session records
2012-09-12 15:57:29,191  INFO SakaiClusterService.Maintenance 
org.sakaiproject.cluster.impl.SakaiClusterService - Closed 1 orphaned 
usage session records

Any idea or suggestion? This is on 2.9.x and Oracle 11g.

Thanks
Omer