STP enhancements on z14 ZR1 Important:  For more information about configuring an STP CTN with three or more  servers, see the  Important Considerations for STP server role assignments  white paper  that is available at the IBM Techdocs Library website.  If the guidelines are not followed, it might result in all the servers in the CTN becoming  unsynchronized. This condition results in a sysplex-wide outage. STP on z14 ZR1 features the following enhancements: The limit was STP Stratum 3 before z14. The extra stratum allows CPCs to operate as part  of CTN at STP stratum level 4, which can avoid the extra complexity and expense of  system reconfiguration.  Warning:  This extra stratum level should be used only as a temporary state during  reconfiguration. Customer should not run with machines at stratum level 4 for extended  periods because of the lower quality of the time synchronization. GLYPH<SM590000> Additional stratum level GLYPH<SM590000> Graphical display of a Coordinated Timing Network (CTN) GLYPH<SM590000> Server Time Protocol Planning Guide , SG24-7280 GLYPH<SM590000> Server Time Protocol Implementation Guide , SG24-7281 GLYPH<SM590000> Server Time Protocol Recovery Guide,  SG24-7380 This graphical display improved the user interface to STP controls. This type of visual  display of the CTN status, which provided a clearer view of CTNs, can avoid outages, such  as a user intentionally took down the CTS, but did not realize the BTS was down. For more information about STP configuration, see the following publications: A pulse per second (PPS) signal can be received from an external time source (ETS) device.  One PPS port is available on each of the two oscillator cards. These cards are installed into  slots LG11 and LG12 of the CPC drawer rear of the frame of z14 ZR1 servers (see  Figure 2-20 on page 49).  Connections to the CPC drawer provide redundancy for continued operation and concurrent  maintenance when a single oscillator card fails. Each oscillator card includes a Bayonet  Neill-Concelman (BNC) connector for PPS connection support, which attaches to two  different ETSs. Two PPS connections from two different ETSs are preferable for redundancy. The time accuracy of an STP-only CTN is improved by adding an ETS device with the PPS  output signal. STP tracks the highly stable accurate PPS signal from ETSs. It maintains  accuracy of 10 µs as measuredat the PPS input of the z14 ZR1 server. If STP uses an NTP  server without PPS, a time accuracy of 100 meters (328 feet) to the ETS is maintained. ETSs  with PPS output are available from various vendors that offer network timing solutions.  Pulse per second input 158  IBM 14 Model ZR1 Technical Guide