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BBCWatcher (talk | contribs) Updated ICF capabilities with z/OS 1.8; more info on the purpose of Parallel Sysplex |
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* 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 specially configured with only coupling facility processors) or integral processors on the mainframes themselves configured as ICFs (Internal Coupling Facilities). Both are popular — there are minor technical advantages and disadvantages between external CF and ICF installations. For achieving highest availability without unnecessary spending, IBM generally recommends combining a single external CF with an ICF. With [[z/OS]] 1.8 and higher an ICF-only implementation is quite viable.
A Parallel Sysplex has at least two CFs or ICFs for redundancy (or at least one of each). Every mainframe participating in a Parallel Sysplex does not need an ICF or its own external CF — mainframes merely attach, via cables, to the external CFs or ICFs.
Server Time Protocol (STP) replaced the Sysplex Timers beginning in 2005 for newer mainframe models. While the Sysplex Timers are physically separate machines, STP is an integral feature within the mainframe itself. With STP and ICFs it is now possible (and common) to construct a complete Parallel Sysplex installation solely with two mainframes and cabling. Moreover, a single mainframe can contain the internal equivalent of a complete physical Parallel Sysplex, so there is no technical requirement to have a multi-frame Parallel Sysplex at least for application testing and development purposes.
Parallel Sysplex enables another major capability: online maintenance. For example, with Parallel Sysplex it is possible (and common) to configure [[DB2]] for z/OS to deliver continuous business service, permitting whole version upgrades and patches while DB2 continues to run and serve users.
==See also==
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