The Server keyword, BUFFER_RUNLENGTH, which defaults to 10, determines how many consecutive write operations are performed while walking a list of buffer/cache pages before the mutex controlling access to the list is released and then reacquired. Releasing the mutex permits other threads to acquire control of the list. If this value is set to a negative value, it is ignored.
For bound server applications, the brunlen member of the ctINIT structure is used to override the default.