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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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==