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Distributed vs. Federated

What's the difference between a distributed and a federated database?
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are you doing this just to annoy marcus?
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God no -- I have better things to do with my time. Here are the definitions from the manual:

Quote:
A distributed relational database consists of a set of tables and other objects that are spread across different but interconnected computer systems. Each computer system has a relational database manager to manage the tables in its environment. The database managers communicate and cooperate with each other in a way that allows a given database manager to execute SQL statements on another computer system.

A federated database is a relational database whose data is stored in multiple data sources (such as separate relational databases). The data appears as if it were all in a single large database and can be accessed through traditional SQL queries. Changes to the data can be explicitly directed to the appropriate data source.
If a federated database is one whose "data is stored in multiple data sources such as separate relational databases," then it seems a distributed database could also be a federated database. I was wondering if they could be further characterized. Perhaps a federated database is administered by only a single instance of a database manager as opposed to having several instances coordinate with each other?

Last edited by db2farmer; 05-17-09 at 17:54.
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Well, if I can believe you that you really mean to cause NO harm to Marcus ... then we can talk Following the definitions you presented, federated is a case of distributed, where you do not have to concern yourself with where the data reside. With federated you reference tables, as usual, by two part names, only in some cases these names are really pointers (nicknames) to tables on remote databases/instances/subsystems. By contrast, without federation, you have to CONNECT to a remote database before using tables there in SQL. Now, that I have done my part in answering your most intriguing questions, please keep in mind that we try to keep those questions that can easily be answered by reading standard manuals, OUT of this forum. Thank you for your future consideration
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Quote:
Originally Posted by db2dummy1
Now, that I have done my part in answering your most intriguing questions, please keep in mind that we try to keep those questions that can easily be answered by reading standard manuals, OUT of this forum. Thank you for your future consideration
So what's the trauma? Those definitions were straight out of a "standard manual" -- one that his highness Marcus pointed me to -- and they failed to sufficiently characterize the difference between the two database models. What's the big deal about posting to a public forum? People are free to help if they want to and they are free to ignore the questions if they want to.

Your distinction about having to explicitly connect to a distributed dabase and not a federated one was very clear and helpful -- but it certainly wasn't covered in the definition from the "standard manual." So, when a "standard manual" is an inadequate resource, where, exactly, do you suggest people to go for clarification?

Last edited by db2farmer; 05-17-09 at 19:11.
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First, tell me which manual you got that from. There are differences in DB2 for Linux/UNIX/Windows and DB2 for z/OS.
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OK, never mind, feel free to post here whatever you like - after all, it is our collective duty and privilege to keep Sir Marcus entertained!!
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Quote:
Originally Posted by Marcus_A
First, tell me which manual you got that from. There are differences in DB2 for Linux/UNIX/Windows and DB2 for z/OS.
DB2 Version 9.5 for Linux, UNIX, and Windows. I followed your link.
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A federated database is one that is enabled and configured so that you can access other databases while connected to a local (or different) database. You can even access more than one database in the same SQL statement using federated support. There is an entire manual on how Federated support works.

Distributed is just a general term that means you have your data in more than one database, and that you have to connect to each one separately to execute SQL against the tables in that database. Some people use distributed to mean all databases on Linux, UNIX, or Windows instead of a mainframe (IBM z/OS).
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There's the love. Thanks. :-)
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Here is a link that is an introduction to IBM Federated Database Technology
. It is a little old (2002) but covers the basics.


IBM Federated Database Technology

One key difference between Distributed and Federated, the Federated data source does not have to be a database. It can be a structured flat file.
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Quote:
Originally Posted by Stealth_DBA
Here is a link that is an introduction to IBM Federated Database Technology
. It is a little old (2002) but covers the basics.
Thanks, it's a good article. Federation actually sounds too complicated to work. The implementation must be a monster.
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