If there is a site or communication failure (for example, a power failure, operating system error, or telecommunication failure) during the process just described, there are different recovery actions, depending on the step at which the failure occurred.
| If the failure occurs at this point in the Two-phase commit process... | Then the participant... |
|---|---|
| before step 4 | rolls back the updates. |
| during step 6 | after the participant has received and logged the coordinator’s commit request, the participant continues with the commit process. |
| after step 4, but before step 6 |
is said to be in-doubt as to whether it should commit or roll back the updates, so it cannot take any unilateral action. The participant must wait for in-doubt resolution to complete the transaction. There are two forms of in-doubt resolution: automatic and manual. They are explained later in further detail. |