It is possible for a failure to occur during the 2PC session. Possible causes include the following:
- A lost communication link between the coordinator (such as CICS) and the participant (such as the database)
- A CICS 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.