IBM Parallel Sysplex: Difference between revisions

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| publisher = IBM

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</ref> upgrades to exitingexisting models, coupling links for high speed communication and MVS/ESA SP V5.1<ref>{{cite web

| title = IBM MVS/ESA SP Version 5 Release 1 and OpenEdition Enhancements

| id = 294-152

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The Coupling Facility (CF) may reside on a dedicated stand-alone server configured with processors that can run Coupling Facility control code (CFCC), as integral processors on the mainframes themselves configured as ICFs (Internal Coupling Facilities), or less common, as normal LPARs. The CF contains Lock, List, and Cache structures to help with serialization, message passing, and buffer consistency between multiple LPARs.<ref>{{cite web

| title = Coupling Facility Configuration Options

| id = ZSW01971USEN

| author = David Raften

| date = November 2019

| publisher = IBM

| work = Positioning paper

| url = http://www.ibm.com/common/ssi/fcgi-bin/ssialias?infotype=SA&subtype=WH&attachment=ZSW01971USEN.PDF&appname=STGE_ZS_ZS_USEN&htmlfid=ZSW01971USEN

}}

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Databases running on the System z server that can take advantage of this include:

* [[IBM DB2|DB2Db2]]

* [[IBM Information Management System]] (IMS).

* [[Virtual Storage Access Method|VSAM]] (VSARM/RLS)

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* Sysplex Timers (more recently, Server Time Protocol) to synchronize the clocks of all member systems;

* High speed, high quality, redundant cabling;

* Software ([[operating system]] services and, usually, [[middleware]] such as [[IBM DB2|DB2Db2]]).

The Coupling Facility may be either a dedicated external system (a small mainframe, such as a [[System z9]] BC, specially configured with only coupling facility processors) or integral processors on the mainframes themselves configured as ICFs (Internal Coupling Facilities).<ref>{{cite web |url=https://www.pcmag.com/encyclopedia_term/0,2542,t=Coupling%2C2542%2Ct%3DCoupling+Facility&i=40413,00%26i%3D40413%2C00.asp |title=Coupling Facility Definition |publisher=PC Magazine.com |access-date=April 13, 2009 |archive-date=December 2, 2008 |archive-url=https://web.archive.org/web/20081202161800/http://www.pcmag.com/encyclopedia_term/0%2C2542%2Ct%3DCoupling+Facility%26i%3D40413%2C00.asp |url-status=dead }}</ref> It is recommended that at least one external CF be used in a parallel sysplex.<ref>{{cite web |url=http://www-ti.informatik.uni-tuebingen.de/os390/sysplex/sysplex/couplfac.pdf |title=Coupling Facility |access-date=April 13, 2009 |archive-date=July 17, 2011 |archive-url=https://web.archive.org/web/20110717185607/http://www-ti.informatik.uni-tuebingen.de/os390/sysplex/sysplex/couplfac.pdf |url-status=dead }}</ref> It is recommended that a Parallel Sysplex has at least two CFs and/or ICFs for redundancy, especially in a production data sharing environment. Server Time Protocol (STP) replaced the Sysplex Timers beginning in 2005 for System z mainframe models z990 and newer.<ref>{{cite web |title=Migrate from a Sysplex Timer to STP |url=http://publib.boulder.ibm.com/infocenter/zos/v1r9/index.jsp?topic=/com.ibm.zos.r9.e0zm100/sttostp.htm |publisher=IBM |access-date=April 15, 2009 }}</ref> A Sysplex Timer is a physically separate piece of hardware from the mainframe,<ref>{{cite web |title=Sysplex Timer |url=http://www.symmetricom.com/resources/compliance-certifications/sysplex-timer/ |publisher=Symmetricom |access-date=April 15, 2009 }}</ref> whereas STP is an integral facility within the mainframe's microcode.<ref>{{cite web |title=IBM Server Time Protocol (STP) |url=http://www-03.ibm.com/systems/z/advantages/pso/stp.html |archive-url=https://web.archive.org/web/20080613095316/http://www-03.ibm.com/systems/z/advantages/pso/stp.html |url-status=dead |archive-date=June 13, 2008 |publisher=IBM |access-date=April 15, 2009 }}</ref>

With STP and ICFs it is possible to construct a complete Parallel Sysplex installation with two connected mainframes. Moreover, a single mainframe can contain the internal equivalent of a complete physical Parallel Sysplex, useful for application testing and development purposes.<ref>{{cite web |url=http://www.zjournal.com/index.cfm?section=article&aid=308 |title=MVS Boot Camp: IBM Health Checker |first=John E. |last=Johnson |publisher=z/Journal |access-date=April 15, 2009 }}{{dead link|date=January 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

The IBM Systems Journal dedicated a full issue to all the technology components.<ref>{{cite web |url=http://researchweb.watson.ibm.com/journal/sj36-2.html |title=IBM's System Journal on S/390 Parallel Sysplex Clusters |access-date=24 April 2017 |archive-date=9 March 2012 |archive-url=https://web.archive.org/web/20120309150534/http://researchweb.watson.ibm.com/journal/sj36-2.html |url-status=dead }}</ref>

==Server Time Protocol==