IBM Z10 EC manual Enhanced Network Time Protocol NTP client support

The following STP enhancements are available on System z10 and System z9 servers.

The STP feature and the latest Machine Change Levels are required.

Enhanced Network Time Protocol (NTP) client support:

This enhancement addresses the requirements for those who need to provide the same accurate time across het- erogeneous platforms in an enterprise.

The STP design has been enhanced to include support for a Simple Network Time Protocol (SNTP) client on the Support Element. By confi guring an NTP server as the STP External Time Source (ETS), the time of an STP-only Coordinated Timing Network (CTN) can track to the time provided by the NTP server, and maintain a time accuracy of 100 milliseconds.

Note: NTP client support has been available since October 2007.

Enhanced accuracy to an External Time Source: The time accuracy of an STP-only CTN has been improved by adding the capability to confi gure an NTP server that has a pulse per second (PPS) output signal as the ETS device. This type of ETS device is available worldwide from sev- eral vendors that provide network timing solutions.

STP has been designed to track to the highly stable, accurate PPS signal from the NTP server, and maintain an accuracy of 10 microseconds as measured at the PPS input of the System z server. A number of variables such as accuracy of the NTP server to its time source (GPS, radio signals for example), and cable used to connect the PPS signal will determine the ultimate accuracy of STP to Coordinated Universal Time (UTC).

In comparison, the IBM Sysplex Timer is designed to maintain an accuracy of 100 microseconds when attached to an ETS with a PPS output. If STP is confi gured to use

a dial-out time service or an NTP server without PPS, it is designed to provide a time accuracy of 100 milliseconds to the ETS device.

For this enhancement, the NTP output of the NTP server has to be connected to the Support Element (SE) LAN, and the PPS output of the same NTP server has to be con- nected to the PPS input provided on the External Time Reference (ETR) feature of the System z10 or System z9 server.

Continuous availability of NTP servers used as Exter-

nal Time Source: Improved External Time Source (ETS) availability can now be provided if you confi gure different NTP servers for the Preferred Time Server (PTS) and the Backup Time Server (BTS). Only the PTS or the BTS can be the Current Time Server (CTS) in an STP-only CTN. Prior to this enhancement, only the CTS calculated the time adjustments necessary to maintain time accuracy. With this enhancement, if the PTS/CTS cannot access the NTP server or the pulse per second (PPS) signal from the NTP server, the BTS, if confi gured to a different NTP server, may be able to calculate the adjustment required and propagate it to the PTS/CTS. The PTS/CTS in turn will per- form the necessary time adjustment steering.

This avoids a manual reconfi guration of the BTS to be the CTS, if the PTS/CTS is not able to access its ETS. In an ETR network when the primary Sysplex Timer is not able to access the ETS device, the secondary Sysplex Timer takes over the role of the primary - a recovery action not

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