Limits the number of file descriptors the library will open concurrently when flushing dirty pages from the cache.
                 The syntax of this parameter in the DB_CONFIG file is a
                 single line with the string
                 set_max_openfd, one or more whitespace
                 characters, and the number of open file descriptors. 
            
For more information, see DbEnv::get_mp_max_openfd().