If your Splunk environment is properly configured, you can find memory usage with this:
tag=performance tag=memory
| stats max(eval(100*mem_used/mem)) as mem_used_percent by host
| where mem_used_percent>90
This isn't the best place to discuss AppDynamics, but you can use the machine agent to collect basic hardware metrics, reports to display them, and health rules to alert on them. Extended metrics require a Server Visibility license.
