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Z16’s Direct-Connect for STP Feature

By Brittany Ross posted Fri December 02, 2022 02:08 PM



With the release of IBM’s latest mainframe, IBM z16, a new feature is introduced – an enhanced method for connecting to a CTN’s external time reference. This new feature enables users to connect the CEC directly to PTP or NTP external time references through a data center network. Now, PTP or NTP traffic comes into the CEC through Ethernet connectivity to a new adapter that features hardware timestamping capabilities, allowing IBM z16 to take full advantage of the accuracy of PTP. With these new enhancements, STP is capable of significantly enhanced accuracy to UTC compared to previous IBM Z machines, with the potential to eliminate the need for PPS connectivity in the future. More information on this new timing feature, as well as all the other new features introduced with IBM’s latest Z system can be found here in the z16 announcement.


To enable the use of the new Direct to CEC PTP feature, you must have the following support:

  • IBM z16 MCL P30716.009 or later
  • APAR OA60036 for z/OS which updates the IEA386I command response message to the z/OS 'D ETR' command to display the new ETS timing mode.


More information on Direct to CEC connectivity, including how to set it up, can be found in the following Redbooks:


Our Experience:

With the release of z15 back in 2020, we wrote a blog post about the PTP timing source being introduced to the Sysplex Time Protocol (STP) for an IBM Z Coordinated Timing Network (CTN), which details our initial setup & configuration of the PTP feature. That blog post can be found here.


To run STP with an external time source (NTP or PTP) on z16, the external time source was plugged directly into zPET's z16 at locations CPC0 - A10BCTL1-J3 and CPC1 - A15BCTL1-J3. When we installed the support for the direct to CEC timing feature and connected our z16 to our timing network, we found there were two ways we could be able to identify we were using the new connection option -- through the HMC using the ‘Manage System Time’ task and by issuing the ‘D ETR’ command on z/OS.



On the HMC, start by selecting the ‘Manage System Time’ task, which will take you to your CTN network diagram. In the upper right-hand corner of the ‘Manage System Time’ task screen, there is an option to view current time details. Clicking that option resulted in a pop-up window with 2 pages. On the second page, the CTN time source is noted, which identified the timing connection we were using. In the screenshot below, you will be able to see that the CTN timing source is a direct PTP connection:



In addition to the HMC ‘Manage System Time’ task, we were also able to see what type of timing connection we were using by issuing the ‘D ETR’ command from any of our z/OS LPARs running in our timing network that has the support installed. The ‘ETS ID’ text in the IEA386I message text has a D in front of any timing connection directly connected to the CEC. For example, the following screenshot is the output received after issuing the D ETR command, with the z16 connected directly to the timing network via a PTP connection:

More information on the D ETR command can be found here. Additionally, information about the IEA386I command response message can be found here.

For more information on IBM’s new z16 system & all the new features and upgrades it has to offer, please see the IBM z16 Technical Guide.