Brown University's tn3270x provides secure 3270 emulation for OS X!! Configuring this free and easy software is described in this webpage.

If you are using an earlier version of tn3270x on your Mac,

please install the latest version (3.1.6) to be able to access z/OS 1.7.

• You need to have Administrator access on your Mac to install tn3270x.
• It is Mac OS X only.
• Download tn3270 3.1.6 version and Install
  Available from Brown University. You may want to make a Desktop alias for it.
• Start tn3270x.
• In the Connection window that opens enter the appropriate domain name, depending on the LPAR to which you want to connect.

• For Window Title enter a descriptive name because you'll be saving this configuration later.
• Click the Screen Format icon.

• Click the 27x132 (Model 5) button then click OK.
• Back at the Connection window click the Special icon.

• On the second line of the window that opens click the SSL button, then click OK.
• Back in the Connection window click the Open Connection button. Before you actually log in, under File, choose Save Settings As and save your configuration under the Window Title you set earlier.
• Proceed with your log in.
• Next time you need to log in, start tn3170x, click on the Settings File button, browse for your configuration, double-click it to open it, then click the Open Connection button.