Most systems allow suchwrites to take place only after the transaction has entered
the committed state. One way to implement such a scheme is for the database
system to store any value associated with such external writes temporarily in
a special relation in the database, and to perform the actual writes only after
the transaction enters the committed state. If the system should fail after the
transaction has entered the committed state, but before it could complete the
external writes, the database system will carry out the external writes (using the
data in nonvolatile storage) when the system is restarted.