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Glossary of Terms

local transaction

Transactions that are local to a single resource manager only; for example a transaction that relates to only one database.

distributed transaction

Transactions that are demarcated and coordinated by an external Transaction Manager via the Two Phase Commit Protocol across multiple resource managers. Also known as global transactions.

global transactions

See distributed transactions.

transaction branches

Each resource manager's internal unit of work in support of a global transaction is part of exactly one transaction branch. Each Global Transaction Identifier (GTRID or XID) that the transaction manager gives to the resource manager identifies both a distributed transaction and a specific branch.

heuristic decision

An heuristic decision (or heuristic completion) occurs when a resource makes a unilateral decision during the completion stage of a distributed transaction to commit or rollback updates. This can leave distributed data in an indeterminate state. Network failures or transaction timeouts are possible causes for a heuristic decision.

HeuristicRollback

One resource participating in a transaction decided to autonomously rollback its work, even though it agreed to prepare itself and wait for a commit decision. If the Transaction Manager decided to commit the transaction, the resource's heuristic rollback decision was incorrect, and might lead to an inconsistent outcome since other branches of the transaction were committed.

HeuristicCommit

One resource participating in a transaction decided to autonomously commit its work, even though it agreed to prepare itself and wait for a commit decision. If the Transaction Manager decided to rollback the transaction, the resource's heuristic commit decision was incorrect, and might lead to an inconsistent outcome since other branches of the transaction were rolled back.

HeuristicMixed

The Transaction Manager is aware that a transaction resulted in a mixed outcome, where some participating resources committed and some rolled back. The underlying cause was most likely heuristic rollback or heuristic commit decisions made by one or more of the participating resources.

HeuristicHazard

The Transaction Manager is aware that a transaction might have resulted in a mixed outcome, where some participating resources committed and some rolled back. But system or resource failures make it impossible to know for sure whether a Heuristic Mixed outcome definitely occurred. The underlying cause was most likely heuristic rollback or heuristic commit decisions made by one or more of the participating resources.

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