IBM Parallel Sysplex: Difference between revisions

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==Parallel Sysplex==

[[File:GDPS.svg|thumb|300px|Schematic representation of a Parallel Sysplex]]

The forerunner to Parallel Sysplex was '''Virtualintroduced Coupling''',with athe techniqueaddition whichof allowed up to 12the [[IBMCoupling ESA/390Facility]] systems(CF) towith executecoupling jobslinks infor parallel.high speed Thecommunication, truewith ParallelMVS/ESA SysplexV5.1 wasoperating introducedsystem support, together with then-newthe mainframe models in April 1994.<ref>http://www.redbooks.ibm.com/redbooks/pdfs/sg244356.pdf System/390 Parallel Sysplex Performance - IBM Redbook. Retrieved 17-09-2007.</ref>

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>http://www.ibm.com/common/ssi/fcgi-bin/ssialias?infotype=SA&subtype=WH&attachment=ZSW01971USEN.PDF&appname=STGE_ZS_ZS_USEN&htmlfid=ZSW01971USEN Coupling Facility Configuration Options .</ref>

The primary goal of a Parallel Sysplex is to provide data sharing capabilities, allowing multiple databases for direct reads and writes to shared data. This can provide benefits of

* Help remove single points of failure within the server, LPAR, or subsystems

* Application Availability

* Single System Image

* Dynamic Session Balancing

* Dynamic Transaction Routing

* Scalable capacity

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

* [[DB2]]

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

* VSAM (VSARM/RLS)

* IDMS

* AdaPlex

* DataCom

* Oracle

Other components can take use the Coupling Facility to help with system management, performance, or reduced hardware requirements. Called “Resource Sharing,” users include:

* Catalog – shared catalogs to improve performance by reducing I/O to a catalog data set on disk

* CICS – Using the CF to provide a sharing and recovery capabilities for named counters, data tables, or transcient data

* DFSMShsm – Workload balancing for data migration workload

* GRS Star – Reduced CPU and response time performance for data set allocation.

Tape Switching uses the GRS structure to provide sharing of tape units between z/OS images.

* Dynamic CHPID Management (DCM), and I/O priority management

* JES2 Checkpoint – Provides improved access to a multisystem checkpoint

* Operlog / Logrec – Merged multisystem logs for system management

* RACF – shared data set to simplify security management across the Parallel Sysplex

* WebSphere MQ – Shared message queues for availability and flexibility

* WLM - provides support for

Intelligent Resource Director (IRD) to extends the z/OS Workload Manager to help manage CPU and I/O resources across multiple LPARs within the Parallel Sysplex. Functions include LPAR CPU management, IRD.

Multi-system enclave management for improved performance

* XCF Star – Reduced hardware requirements and simplified management of XCF communication paths

Major components of a Parallel Sysplex include:

* [[Coupling Facility]] (CF or ICF) hardware, allowing multiple processors to share, cache, update, and balance data access;

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* High speed, high quality, redundant cabling;

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

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=http://www.pcmag.com/encyclopedia_term/0,2542,t=Coupling+Facility&i=40413,00.asp |title=Coupling Facility Definition |publisher=PC Magazine.com |accessdate=April 13, 2009 }}</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 |accessdate=April 13, 2009 }}</ref> AIt is recommended that a Parallel Sysplex has at least two CFs and/or ICFs for redundancy, especially in a production data sharing environment. EveryServer mainframeTime participatingProtocol (STP) replaced the Sysplex Timers beginning in 2005 for System z mainframe models z990 and newer.<ref>{{cite web |title=Migrate from a ParallelSysplex Timer to STP |url=http://publib.boulder.ibm.com/infocenter/zos/v1r9/index.jsp?topic=/com.ibm.zos.r9.e0zm100/sttostp.htm |publisher=IBM |accessdate=April 15, 2009 }}</ref> A Sysplex doesTimer notis needa anphysically ICFseparate orpiece itsof ownhardware externalfrom CF&nbsp;&mdash;the mainframesmainframe<ref>{{cite merelyweb attach|title=Sysplex Timer |url=http://www.symmetricom.com/resources/compliance-certifications/sysplex-timer/ |publisher=Symmetricom |accessdate=April 15, via2009 cables}}</ref>, towhereas STP is an integral facility within the externalmainframe's CFsmicrocode.<ref>{{cite orweb ICFs|title=IBM Server Time Protocol (STP) |url=http://www-03.ibm.com/systems/z/advantages/pso/stp.html |publisher=IBM |accessdate=April 15, 2009 }}</ref>

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 |accessdate=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 |accessdate=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 |publisher=IBM |accessdate=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 |accessdate=April 15, 2009 }}</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 |accessdate=1997 }}</ref>

==Geographically Dispersed Parallel Sysplex==