3 Phase Commit [3PC]

According to the Wiki - paper "A Formal Model of Crash Recovery in a Distributed System" of Dale Skeen and Michael Stonebraker is main source about 3PC [PDF or PDF].

Paper contains very good analisys and critique of 2PC and definition of 3PC.

There are else some research of thin boundary between Сonsistency and Partition Tolerance (like CAP-Theorem):
"Theorem #2: Rules 1 and 2 are sufficient for designing protocols resilient to a single site failure.
Theorem #3: There exist no protocol using independent recovery that is resilient to arbitrary failures by two sites.
Theorem #4: There exist no protocol resilient to a network partitioning when messages are lost.
Theorem #5: Design Rules 3 and 4 are nesessary and sufficient for making protocols resilient to a partition in a two-site site protocol.
Corollary #6: There exist multisite protocols that are resilient to a simple partition when undeliverable messages are returned to the sender.
Corollary #7: Knowlege of which messages were undelivered at the time the network fails is nesessary and sufficient for recovering from simple partitions.
Theorem #8: There exist no protocol resilient to a multiple partition."

BASE: An Acid Alternative

Cтатья. там же есть ссылка на pdf. Из статьи:
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Conclusion

Scaling systems to dramatic transaction rates requires a new way of thinking about managing resources. The traditional transactional models are problematic when loads need to be spread across a large number of components. Decoupling the operations and performing them in turn provides for improved availability and scale at the cost of consistency. BASE provides a model for thinking about this decoupling.