That is exactly what I meant, but I did not mean to imply that the cost was entirely paid in performance or that it couldn't be mitigated by other factors. The cost of using rollback segments includes additional disk space and memory used, which impact performance. There tends to be a minimal overall performance hit because of reduced blocking so that tends to be a wash. Yes, Oracle does well on the TPC benchmarks (as do DB2 and SQL Server) but the biggest "cost" I see with the Oracle approach is management. Our Oracle DBA's spent considerable time managing and monitoring the rollback segments. Our SQL Server DBA's spent much less time dealing with blocking problems.
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If most people are not willing to see the difficulty, this is mainly because, consciously or unconsciously, they assume that it will be they who will settle these questions for the others, and because they are convinced of their own capacity to do this. -Friedrich August von Hayek
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