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Time synchronization and time accuracy on z10 EC
If you require time synchronization across multiple servers
(for example you have a Parallel Sysplex environment) or
you require time accuracy either for one or more System
z servers or you require the same time across heteroge-
neous platforms (System z, UNIX, AIX
®
, etc.) you can meet
these requirements by either installing a Sysplex Timer
Model 2 (9037-002) or by implementing Server Time Proto-
col (STP).
The Sysplex Timer Model 2 is the centralized time source
that sets the Time-Of-Day (TOD) clocks in all attached
servers to maintain synchronization. The Sysplex Timer
Model 2 provides the stepping signal that helps ensure
that all TOD clocks in a multi-server environment incre-
ment in unison to permit full read or write data sharing with
integrity. The Sysplex Timer Model 2 is a key component of
an IBM Parallel Sysplex environment and a GDPS
®
avail-
ability solution for On Demand Business.
The z10 EC server requires the External Time Reference
(ETR) feature to attach to a Sysplex Timer. The ETR fea-
ture is standard on the z10 EC and supports attachment
at an unrepeated distance of up to three kilometers (1.86
miles) and a link data rate of 8 Megabits per second.
The distance from the Sysplex Timer to the server can be
extended to 100 km using qualifi ed Dense Wavelength
Division Multiplexers (DWDMs). However, the maximum
repeated distance between Sysplex Timers is limited to
40 km.
Server Time Protocol (STP)
STP is a message-based protocol in which timekeeping
information is transmitted between servers over externally
defi ned coupling links. ICB-4, ISC-3, and Infi niBand cou-
pling links can be used to transport STP messages.
Server Time Protocol (STP) Enhancements
STP confi guration and time information restoration
after Power on Resets (POR) or power outage:
This
enhancement delivers system management improvements
by restoring the STP confi guration and time information
after Power on Resets (PORs) or power failure that affects
both servers of a two server STP-only Coordinated Timing
Network (CTN). To enable this function the customer has to
select an option that will assure than no other servers can
join the two server CTN. Previously, if both the Preferred
Time Server (PTS) and the Backup Time Server (BTS)
experienced a simultaneous power outage (site failure),
or both experienced a POR, reinitialization of time, and
special roles (PTS, BTS, and CTS) was required. With this
enhancement, you will no longer need to reinitialize the
time or reassign the roles for these events.
Preview - Improved STP System Management with
new z/OS Messaging:
This is a new function planned to
generate z/OS messages when various hardware events
that affect the External Time Sources (ETS) confi gured for
an STP-only CTN occur. This may improve problem deter-
mination and correction times. Previously, the messages
were generated only on the Hardware Management Con-
sole (HMC).
The ability to generate z/OS messages will be supported
on IBM System z10 and System z9 servers with z/OS 1.11
(with enabling support rolled back to z/OS 1.9) in the
second half of 2009.
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