Dead-Locks

Prevention, detection, resolution.

What are the semantics needed to resolve them?

At these levels, it is not possible to compare the conflicting parties (transactions, but also tasks):

• Do they really conflict?
• Do they actually collaborate? Because of information hiding, they may not know each other, though still concur to a common goal... If they do, they should maybe share a same view of the resource, even if not fully consistent. Otherwise, they must be isolated.
• How much have they invested so far (what is the price of aborting them)? Have they save-points, allowing for partial rollbacks? Would these partial rollbacks suffice?
• How far are they from completion (how long should one wait for them to bring the system back to a consistent state)?
• What is their priority? Their goal?

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