FAILSAFE : Node 1 frequently failover to Node 1

Type                        Software
O/S                           Microsoft Windows 2003 Server
Database                Oracle 10g Enterprises Edition Release 10.2.0.3.0 - 32bit Production
                                 With the partitioning, OLAP and Oracle Data Mining Options
Failsafe                   Oracle Fail Safe Release 3.4.1 for Microsoft Windows (32-bit)

No of Nodes            2

Connection between nodes  Fibre cable

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Hi All,
   I have problem with cluster environment running on Oracle Failsafe. The system was 90% stable for nearly a year. It has problem initially that Node 1 occassionally failover to Node 2 without unknown reason. It was so rare that we did not receive any ongoing complain from customer. Lately for the past 2 weeks, it seems that the problem become severe (failover every 2 days). Usually the failover happen in the morning when nobody accessing the database. After diagnosing the logs "c:\windows\cluster\cluster.log" we do not seems to find any lead to resolve the issue. So far we are suspecting