Sorry, case closed, it was the user monitoring script itself problem
We have 4 x EMC Brocade DS300B Switches that now having intermittent Power Supply and Temperature Problem reported several times a day, but nothing is found in the errdump event log.  We have SiteScope regularly SNMP poll the 4 x switches every 10 minutes and found that there's the following SNMP Error:- 1) PowerSupply-1 fault 2) Temperature high than 35 degree (Normal Temperature is 20~22 Degree Celsius)  I started to wonder if it's the DS300B Product problem or its SNMP agent because it can't be 4 x Switches having such problem.  We used the EMC 6505 before but have never experienced such intermittent problem.
EMC Brocade DS300B Switch SNMP Poll Problem