Thursday, March 24, 2005

Re: Transaction Model Choices

Dan, are you referring to two phrase locking or two phrase commit? If my memory is not failing me, the two phrase locking refers to the database locking model which ensures serializable transaction. While the two phrase commit is referring to how distributed system can collectively make a decision. It can be used for distributed transaction, but not limited to that.

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1 comment:

PetrolHead said...


I was actually trying to make the point that two phase commit and two-phase locking are entirely different things and one needn't imply the other.

I was also trying to hint that two phase locking is just one way in which a database might achieve transaction serialization. In fact, databases, internally quite often have in-built (and even default) optimistic concurrency based on timestamps.

Lastly, you remember correctly that two phase commit is indeed for distributed consensus but it is quite independent of and nor does it require, two-phase locking.