See ObjectRelationalImpedanceMismatch, ObjectRelationalImpedanceMismatchDoesNotExist, ArgumentsThatTheObjectRelationalImpedanceMismatchDoesNotExist, TablesAndObjectsAreTooDifferent, ObjectRelationalMappingCostsTimeAndMoney
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I thought it is good to put here some useful links to serve as a background for the discussion.
Please help me to add, probably I'll miss a lot of useful links.
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Naphtali Rishe's : SemanticBinaryModel.  
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ChrisDate and HughDarwen: TheThirdManifesto. 

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ChrisDate: AnIntroductionToDatabaseSystems
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FabianPascal : Practical Issues in Database Management Systems

ISBN: 0-201-48555-9
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http://www.dbdebunk.com, "The Forum Where Database Matters Are Set Straight"
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'''Links on transaction processing'''

A very good book on basic concepts of concurrency control, trnsaction management and recovery is found at:
http://research.microsoft.com/pubs/ccontrol/

The famous ''isolation levels'' are discussed (aside from vitually every DBMS documentation) at
http://www.pmg.lcs.mit.edu/~adya/pubs/published.pdf

and 

http://www.cs.umb.edu/~poneil/iso.ps

TransactionProcessingConceptsAndTechniques
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On OO side of the story

KyleBrown and BruceWhitenack: CrossingChasms

ScottAmbler: Mapping Objects to Relational Databases http://www.ambysoft.com/mappingObjects.pdf. This paper is a little old and rusty and suffer from obvious flaws. A more elaborate essay you can download from http://www.theserverside.com, see the book in progress there, complex persistence chapter.

EnterpriseJavaBeans is a very good example of how things got derailed because of a psychological impedance mismatch.
You can see the quasi-majority of patterns related to them are supposed to solve a thing that is broken by the specification.

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RelationalWeenie Rants

http://www.geocities.com/tablizer/oorelndx.htm