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This Concept Map, created with IHMC CmapTools, has information related to: ch14 dist flat, a distributed transaction refers to a flat or nested transaction that accesses objects managed by multiple servers contains A flat client transaction completes each of its requests before going on to the next one. Therefore, each transaction accesses servers’ objects sequentially, a distributed transaction refers to a flat or nested transaction that accesses objects managed by multiple servers contains one of the servers is coordinator, it must ensure the same outcome at all of the servers. the ‘two-phase commit protocol’ is the most commonly used protocol for achieving this, nested transaction: In a nested transaction, the top-level transaction can open subtransactions, and each subtransaction can open further subtransactions down to any depth of nesting contains In the nested case, subtransactions at the same level can run concurrently, so T1 and T2 are concurrent, and as they invoke objects in different servers, they can run in parallel., Flat and nested distributed transactions contains The join operation it has openTransaction, closeTransaction and abortTransaction openTransaction returns a TID which is passed with each operation so that servers know which transaction is accessing its objects The Coordinator interface provides an additional method, join, which is used whenever a new participant joins the transaction: join(Trans, reference to participant)informs a coordinator that a new participant has joined the transaction Trans. the coordinator records the new participant in its participant list. the fact that the coordinator knows all the participants and each participant knows the coordinator will enable them to collect the information that will be needed at commit time., Flat and nested distributed transactions contains a distributed transaction refers to a flat or nested transaction that accesses objects managed by multiple servers, at the end, it will be responsible for committing or aborting it each server managing an object accessed by the transaction is a participant - it joins the transaction a participant keeps track of objects involved in the transaction at the end it cooperates with the coordinator in carrying out the commit protocol note that a participant can call abortTransaction in coordinator contains Each server is shown with a participant, which joins the transaction by invoking the join method in the coordinator, The coordinator of a flat distributed transaction Servers execute requests in a distributed transaction when it commits they must communicate with one another to coordinate their actions a client starts a transaction by sending an openTransaction request to a coordinator in any server it returns a TID unique in the distributed system (e.g. server ID + local transaction number) contains at the end, it will be responsible for committing or aborting it each server managing an object accessed by the transaction is a participant - it joins the transaction a participant keeps track of objects involved in the transaction at the end it cooperates with the coordinator in carrying out the commit protocol note that a participant can call abortTransaction in coordinator, In the nested case, subtransactions at the same level can run concurrently, so T1 and T2 are concurrent, and as they invoke objects in different servers, they can run in parallel. contains requests can be run in parallel - with several servers, the nested transaction is more efficient, a distributed transaction refers to a flat or nested transaction that accesses objects managed by multiple servers contains When a distributed transaction comes to an end either all of the servers commit the transaction or all of them abort the transaction., a distributed transaction refers to a flat or nested transaction that accesses objects managed by multiple servers contains nested transaction: In a nested transaction, the top-level transaction can open subtransactions, and each subtransaction can open further subtransactions down to any depth of nesting