IBM Z10 BC manual Continuous Availability of NTP servers used as Exter

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 always accepted by some customers. The STP design provides continuous availability of ETS while maintaining the special roles of PTS and BTS as – signed by the cus- tomer.

The availability improvement is available when the ETS is confi gured as an NTP server or an NTP server using PPS.

NTP Server on Hardware Management Console: Improved security can be obtained by providing NTP server support on the HMC. If an NTP server (with or with- out PPS) is confi gured as the ETS device for STP, it needs to be attached directly to the Support Element (SE) LAN. The SE LAN is considered by many users to be a private dedicated LAN to be kept as isolated as possible from the intranet or Internet.

Since the HMC is normally attached to the SE LAN, pro- viding an NTP server capability on the HMC addresses the potential security concerns most users may have for

attaching NTP servers to the SE LAN. The HMC, via a separate LAN connection, can access an NTP server avail- able either on the intranet or Internet for its time source. Note that when using the HMC as the NTP server, there is no pulse per second capability available. Therefore, you should not confi gure the ETS to be an NTP server using PPS.

Enhanced STP recovery when Internal Battery Feature

is in use: Improved availability can be obtained when power has failed for a single server (PTS/CTS), or when there is a site power outage in a multi site confi guration where the PTS/CTS is installed (the site with the BTS is a different site not affected by the power outage).

If an Internal Battery Feature (IBF) is installed on your System z server, STP now has the capability of receiving notifi cation that customer power has failed and that the IBF is engaged. When STP receives this notifi cation from a server that has the role of the PTS/CTS, STP can automati- cally reassign the role of the CTS to the BTS, thus automat- ing the recovery action and improving availability.

STP configuration and time information saved across

Power on Resets (POR) or power outages: This enhancement delivers system management improvements by saving the STP confi guration across PORs and power failures for a single server STP-only CTN. Previously, if the server was PORed or experienced a power outage, the time, and assignment of the PTS and CTS roles would have to be reinitialized. You will no longer need to reinitial- ize the time or reassign the role of PTS/CTS across POR or power outage events.

Note that this enhancement is also available on the z990 and z890 servers.

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