This was fixed in LMDB 0.9.9, except: If both O_DIRECT and F_NOCACHE are #defined, both are used. Looks a bit strange. Maybe just one should be used in that case. (Which?) Also I'm still wondering if env_open needs to fail if F_NOCACHE fails. Anyway, maybe it should be something like this. The "else {}" is in case O_DIRECT is an unsupported dummy definiton: #ifdef O_DIRECT if ((rc = fcntl(newfd, F_GETFL)) != -1) (void) fcntl(newfd, F_SETFL, rc | O_DIRECT); else #endif { #ifdef F_NOCACHE /* __APPLE__ */ (void) fcntl(newfd, F_NOCACHE, 1); #endif } -- Hallvard