IBM Z10 EC manual Time synchronization and time accuracy on z10 EC, Server Time Protocol STP

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 configuration 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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