IBM z13s Technical Manual page 50

To support an upgrade from one CFCC level to the next, different levels of CFCC can coexist
in the same sysplex while the coupling facility LPARs are running on different servers. CF
LPARs that run on the same server share the CFCC level.
A CF running on a z13s server (CFCC level 21) can coexist in a sysplex with CFCC levels 17
and 19. Review the CF LPAR size by using the CFSizer tool:
http://www.ibm.com/systems/z/cfsizer
Server Time Protocol facility
If you require time synchronization across multiple IBM z Systems servers, you can
implement Server Time Protocol (STP). STP is a server-wide facility that is implemented in
the LIC of z Systems CPCs (including CPCs running as stand-alone coupling facilities). STP
presents a single view of time to PR/SM and provides the capability for multiple servers to
maintain time synchronization with each other.
Any z Systems CPC can be enabled for STP by installing the STP feature. Each server that
must be configured in a Coordinated Timing Network (CTN) must be STP-enabled.
The STP feature is the supported method for maintaining time synchronization between
z Systems images and coupling facilities. The STP design uses the CTN concept, which is a
collection of servers and coupling facilities that are time-synchronized to a time value called
Coordinated Server Time (CST).
Network Time Protocol (NTP) client support is available to the STP code on the z13, z13s,
zEC12, zBC12, z196, and z114 servers. With this function, the z13, z13s. zEC12, zBC12,
z196, and z114 servers can be configured to use an NTP server as an external time source
(ETS).
This implementation answers the need for a single time source across the heterogeneous
platforms in the enterprise. An NTP server becomes the single time source for the z13, z13s,
zEC12, zBC12, z196, and z114 servers, as well as other servers that have NTP clients, such
as UNIX and Microsoft Windows systems.
The time accuracy of an STP-only CTN is improved by using, as the ETS device, an NTP
server with the pulse per second (PPS) output signal. This type of ETS is available from
various vendors that offer network timing solutions.
Improved security can be obtained by providing NTP server support on the HMC for the SE.
The HMC is normally attached to the private dedicated LAN for z Systems maintenance and
support. For z13s and zBC12 server, authentication support is added to the HMC NTP
communication with NTP time servers. In addition, TLS/SSL with Certificate Authentication is
added to the HMC/SE support to provide a secure method for connecting clients to z
Systems.
Attention: A z13s server cannot be connected to a Sysplex Timer and cannot join a Mixed
CTN.
If a current configuration consists of a Mixed CTN, the configuration must be changed to an
STP-only CTN before z13s integration. z13s servers can coexist only with z Systems
CPCs that do not have the Exernal Time Reference (ETR) port capability.
Support has been added to enable STP communications to occur by using the ICA SR (new
for z13s servers).
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IBM z13s Technical Guide