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.