Syntax options:

    WAIT | NOWAIT | DEFAULT WAIT

    Specifies what wait state is used when a reference to NEXTVAL
    is used. A reference to NEXTVAL for a sequence may require
    synchronization with other users of the sequence. When you
    specify DEFAULT WAIT, the wait state (WAIT or NOWAIT) of the
    current transaction is used. This may mean that no waiting is
    performed during a NOWAIT transaction.

    If you specify WAIT (the default) for the sequence, then
    regardless of the wait state set for the current transaction, all
    synchronization waits for the next value. This is the recommended
    setting if the application uses NOWAIT transactions. The current
    WAIT timeout interval defined for the transaction or database is
    used.

    If you specify NOWAIT for the sequence, then regardless of the
    current transaction setting, all synchronization does not wait
    for the next value.