It is possible for a failure to occur during the 2PC session during one of the following circumstances:
- The communication link between the coordinator, such as IMS, and the participant, such as the database, is lost.
- There is an IMS system crash.
- A participant, such as DB2, experiences a system failure.
When the electrical power, system, or communication line is restored after a failure, the coordinator reconciles existing activity logs from the coordinator and the participants.
If the logs cannot be reconciled, then in-doubt resolution is necessary.
There are two forms of in-doubt resolution: automatic and manual.