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CLOCKxx member considerations when in Local Timing Mode



Document Author:

Gregory Hutchison


Document ID:

FLASH10576


Doc. Organization:

Advanced Technical Sales


Document Revised:

02/25/2010


Product(s) covered:

Sysplex Timer; z9-109; z9 BC; z9 EC; zSeries 890; zSeries 990







Abstract: This Flash is intended to draw attention to the informational APAR OA21009. This information is also documented in SA22-7592, Z/OS MVS Initialization and Tuning Reference.


When z/OS is enabled for STP via the PTF for APAR OA13344 (integrated into z/OS V1.8 and higher), the CLOCKxx member is automatically updated to include support for STP, by default. That is, the following parameters are active even if they are NOT coded in the CLOCKxx member.
  • STPMODE YES
  • STPZONE YES


Note the following consequences and take appropriate action on your CLOCKxx member.
  • If the z/OS system image is running on a server that is in LOCAL timing mode, then STPMODE NO should be explicitly coded to avoid messages IEA888A and IEA381I during system initialization.
    If ETRMODE NO and STPMODE YES (the default) is specified z/OS will issue IEA888A to prompt the operator to set the TOD clock during system initialization. This will occur regardless of whether OPERATOR PROMPT or NOPROMPT has been specified.
    IEA888A is issued as system initialization has detected that STPMODE YES was requested but STP is not available. The operator is prompted to notify that local Server time is being used and allow the time to be adjusted if required. IEA888A is issued regardless of whether OPERATOR PROMPT or NOPROMPT is specified in CLOCKxx.

In addition -
If ETRMODE YES is specified the following message is issued:
IEA261I NO ETR PORTS ARE USABLE. CPC CONTINUES TO RUN IN LOCAL MODE.

If ETRMODE NO and STPMODE YES (default) is specified the following message is issued:
IEA381I THE STP FACILITY IS NOT USABLE. SYSTEM CONTINUES IN LOCAL TIMING MODE

Notes:
Be aware that any changes to the CLOCKxx member will require an IPL before the changes can take affect. Customers may not want to change the default STPMODE YES to NO just because they are not ready yet to migrate to STP, because when they are ready they will need to re-IPL with STPMODE YES.

If the z/OS system image is running with SIMETRID, this FLASH is not relevant, as ETRMODE and STPMODE are ignored when SIMETRID is specified.

If the z/OS system image is running on a server that is in ETR timing mode, and both STPMODE and ETRMODE have been specified as YES, z/OS uses ETRMODE YES.

If the z/OS system image is running on a server that is in STP timing mode, and both STPMODE and ETRMODE have been specified as YES, z/OS uses STPMODE YES.


NameDescriptionUsage Notes
Local Timing ModeThe TOD clock has been initialized to a local time and is being stepped at the rate of the local hardware oscillator.The server is not part of a synchronized timing network.
ETR Timing ModeThe TOD clock has been initialized to the Sysplex Timer and is being stepped by stepping signals from the Sysplex Timer.The server must be part of an ETR network.
STP Timing ModeThe TOD clock has been initialized to Coordinated Server Time (CST) and is being stepped at the rate of the local hardware oscillator, and is steered so as to maintain, or attain, synchronization with CST.The server must be part of an STP network.


General Preventive Service Planning (PSP) Information:
Customers should look in the associated hardware PSP subset. The upgrade will be: xxxxDevice and the subset will be xxxx/ZOS where xxxx is one of the server unit numbers which support STP (xxxx = 2094, 2096, 2084, 2086).

To simplify the identification of PTFs needed to support Server Timer Protocol, a functional PSP bucket has been created. You can use the Technical Help Database for Mainframe Preventive Service Planning Buckets (http://www14.software.ibm.com/webapp/set2/psp/srchBroker) and the Enhanced PSP Tool to reconcile the recommended service for the STP function and the hardware device against you systems target zones.

The web site provides a search capability, as well as pull down lists for types of PSP buckets. Scroll down to the "Find the bucket by type, category, and release" heading, select 'Function' for the Type field, select 'STP' for the Category field, and click Go.

Note: The Enhanced PSP Tool is scheduled to be removed after December 31, 2010.



Classification:

Hardware; Software

Category:

Installation and Migration




Platform(s):

IBM System z Family



O/S:

MVS; z/OS

Keywords:

CLOCKxx, STP, Server Time Protocol, ETR, 9037

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