> For the complete documentation index, see [llms.txt](https://docs.postgresql.tw/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.postgresql.tw/internals/transactions/two-phase.md).

# 67.4. Two-Phase Transactions \#

PostgreSQL supports a two-phase commit (2PC) protocol that allows multiple distributed systems to work together in a transactional manner. The commands are `PREPARE TRANSACTION`, `COMMIT PREPARED` and `ROLLBACK PREPARED`. Two-phase transactions are intended for use by external transaction management systems. PostgreSQL follows the features and model proposed by the X/Open XA standard, but does not implement some less often used aspects.

When the user executes `PREPARE TRANSACTION`, the only possible next commands are `COMMIT PREPARED` or `ROLLBACK PREPARED`. In general, this prepared state is intended to be of very short duration, but external availability issues might mean transactions stay in this state for an extended interval. Short-lived prepared transactions are stored only in shared memory and WAL. Transactions that span checkpoints are recorded in the `pg_twophase` directory. Transactions that are currently prepared can be inspected using [`pg_prepared_xacts`](/internals/views/view-pg-prepared-xacts.md).

***

原文：[PostgreSQL 18.6 Documentation](https://www.postgresql.org/docs/18/two-phase.html)（英文原文，待翻譯）


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