Two-phase commit

A commit operation is an operation that is all or nothing.

A two phase commit allows data to be written to more than location and for all operations to be rolled back, if one or more of the operation fails.

It does this using a two-phase commit.

Basically....

Phase 1 Each participants resource manager coordinates local operations If successful

 respond "OK" 

If unsuccessful

 either allow a time-out or respond "NOT OK" 

Phase 2 If all participants respond "OK":

 Coordinator instructs participating resource managers to "COMMIT" 
 Participants complete operation

Otherwise:

 Coordinator instructs participating resource managers to "ROLLBACK" 
 Participants complete their respective local undos