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rm disputed and misplaced material. Galli, cited here describes systems as heterogeneous. Recover citations as Further reading. |
Rescuing orphaned refs ("Galli2000" from rev 1059075429; "Chow1997" from rev 1059075429) |
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System management components are software processes that define the node's ''policies''. These components are the part of the OS outside the kernel. These components provide higher-level communication, process and resource management, reliability, performance and security. The components match the functions of a single-entity system, adding the transparency required in a distributed environment.<ref name="Gościński1991"/>
The distributed nature of the OS requires additional services to support a node's responsibilities to the global system. In addition, the system management components accept the "defensive" responsibilities of reliability, availability, and persistence. These responsibilities can conflict with each other. A consistent approach, balanced perspective, and a deep understanding of the overall system can assist in identifying [[diminishing returns]].<!--this sentence is rhetoric. say what is meant. give an example.--> Separation of policy and mechanism mitigates such conflicts.<ref name="Chow1997">{{cite book|last1=Chow|first1=Randy|author2=Theodore Johnson|title=Distributed Operating Systems and Algorithms|url=https://books.google.com/books?id=J4MZAQAAIAAJ|year=1997|publisher=Addison Wesley|isbn=978-0-201-49838-7}}</ref>
===Working together as an operating system===
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* ''Location transparency'' – Location transparency comprises two distinct aspects of transparency, naming transparency and user mobility. Naming transparency requires that nothing in the physical or logical references to any system entity should expose any indication of the entity's ___location, or its local or remote relationship to the user or application. User mobility requires the consistent referencing of system entities, regardless of the system ___location from which the reference originates.<ref name="Sinha1997" />{{rp|20}}
* ''Access transparency'' – Local and remote system entities must remain indistinguishable when viewed through the user interface. The distributed operating system maintains this perception through the exposure of a single access mechanism for a system entity, regardless of that entity being local or remote to the user. Transparency dictates that any differences in methods of accessing any particular system entity—either local or remote—must be both invisible to, and undetectable by the user.<ref name="Gościński1991"/>{{rp|84}}<!--what is the difference between referencing and access?-->
* ''Migration transparency'' – Resources and activities migrate from one element to another controlled solely by the system and without user/application knowledge or action.<ref name="Galli2000">{{cite book|last=Galli|first=Doreen L.|title=Distributed Operating Systems: Concepts and Practice|url=https://archive.org/details/distributedopera00gall |url-access=registration|year=2000|publisher=Prentice Hall|isbn=978-0-13-079843-5}}</ref>{{rp|16}}
* ''Replication transparency'' – The process or fact that a resource has been duplicated on another element occurs under system control and without user/application knowledge or intervention.<ref name="Galli2000" />{{rp|16}}
* ''Concurrency transparency'' – Users/applications are unaware of and unaffected by the presence/activities of other users.<ref name="Galli2000" />{{rp|16}}
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