This function is intended to be used unified overview expiry together with OVERreinit and OVERreplace . OVERreinit reinitialize current overview file. OVERreplace replaces current overview file with new one. OVERgetnum tells the number of file descriptor which is opened as unified overview file. It just tells current overview file, and does not include new overview file.
OVERstore stores overview data into configured unified over- view file.
Index and offset is written into token . OVERretrieve retrieves overview data which is indicated by token . It returns the pointer if the retrieval is success- ful and overlen is set or returns NULL if not. OVERcancel marks token 's overview data is canceled. OVERshutdown calls the shutdown for each configured unified overview then free any resources it has allocated for itself.