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February 01, 2011

Mark Wielaard: New GPG key. Finally created a new GPG key using gnupg. The old one was a DSA/1024 bits one and 8 years old. The new one is a RSA/2048 bits one. I will use the new one in the future to sign any release tarballs I might create. pub 2048R/57816A6A 2011-01-29 Key f...

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February 01, 2011

Andrew Hughes: [SECURITY] IcedTea6 1.7.8, 1.8.5, 1.9.5 Released!. We are pleased to announce a new set of security releases, IcedTea6 1.7.8, IcedTea6 1.8.5 and IcedTea6 1.9.5. This update contains the following security updates: The IcedTea project provides a harness to build the source code from OpenJDK6 u...

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home > news > java technology > carol mcdonald describes locking and concurrency in jpa 2.0

Carol McDonald Describes Locking and Concurrency in JPA 2.0

In her lastest Enterprise Tech Tip, Carol McDonald writes about Locking and Concurrency in Java Persistence 2.0. I'm pointing out Carol's article in Java Today, but I'd also like to talk a bit more about what she covers here. If you haven't done a lot of work with databases, in particular what I'd call "low-level" work on tuning the performance of databases in an enterprise environment, then it's possible that you've never really given much thought to the problems of locking and concurrency. Yet, these are fundamental to the reliablility of database transactions. As Carol says: Locking is a technique for handling database transaction concurrency. When two or more database transactions concurrently access the same data, locking is used to ensure that only one transaction at a time can change the data. Sounds simple enough, right? But, it's not quite that simple, because a single method for performing locking may work well under some conditions, and poorly under others. Carol explains: There are generally two locking approaches: optimistic and pessimistic. Optimistic locking assumes that there will be infrequent conflicts between concurrent transactions, that is, they won't often try to read and change the same data at the same time. In optimistic locking, the objective is to give concurrent transactions a lot of freedom to process simultaneously, but to detect and prevent collis...

Date: September, 15 2009

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