Ernie Gilman of IBM did a very nice presentation on "Top 10 Tips for z/OS Network Performance Monitoring with OMEGAMON". This is a very detailed review of common network challenges and how to analyze them using OMEGAMON For Mainframe Networks.
The session looked at how correlation between key metrics can more quickly isolate performance problems, how to identify how poorly designed end to end applications could be the cause to high z/OS overhead, and how to create a simple view to help identify why TCP/IP connections are randomly being rejected.
Ernie made some very nice custom workspaces to show how to more effectively use the tool.
Here's a link to the presentation: