Database and Client/Server Management Tools

I am trying to understand the differences between the major applications to monitor and control a production Unix, NT and Netware environment. The applications I am aware of are Compuware Ecotools, BMC Patrol, Platinum DB Vision and Univision, Openvision, Legent Agentworks and Tivoli. It looks like there a different class of tools then the SNMP type (Sunnet Manager, HP Openview, IBM Netview 6000) which focus on Physical network management. They seem to focus on Database, System administration and Monitoring, what else ? The mechanism usually seems to be SNMP or RPC. I throught SNMP was unreliable compared to RPC's. Why would somebody control there production DP environment with a unreliable communication mechanism. Are all these tools as stable like the IBM mainframe tools are. I would like to collect as much information as possible on the above. Please share any and all information you can. Thanks in Advance, Geoff (Please also reply directly to me at Premie001@aol.com)