Alert for Cpu, Memory, Disk usage

[Vishal2]

i have 2 servers 

1 is Windows

2 is Unix

The data(Cpu, Memory, Disk usage )on these two servers comes into splunk

my Question is : I need an alert if their usage exceeds 90%. 

[richgalloway]

What have you tried so far?  Do you have a search that returns the resource usage for the servers?  That's the first step.  Once you have a working search, add a clause that discards anything < 90%.  Then save the search as an alert.