[Info-vax] Databases versus RMS

[Johnny Billquist]

On 2012-04-18 15:43, Bob Koehler wrote:
> In article<jmm94e$atj$1 at Iltempo.Update.UU.SE>, Johnny Billquist<bqt at softjar.se>  writes:
>>
>> Even beyond any language issue, or RMS details, the OS can cache and
>> defer actual writes to the disk without you ever knowing about it. Not
>> to mention that disks also cache things...
>>
>
>     OS cache?  Are you dreaming UNIX?  VMS has never cahced any data I
>     cared about without my explicitly telling it to do so.

Really? I find it hard to believe. RSX have done caching of things from 
the disk at that low level since day one. F11ACP do some caching for the 
system, keeping the most recently referenced directories around in a 
cache in the ACP.

Newer versions of RSX also do caching of individual blocks fully 
transparent at the OS level. It's selectable if you want writes to be 
write-back or write-through.

That VMS would have none of this sounds unlikely, as well as very bad 
for performance.

>     Disks that cache should use a non-volatile memory to do so, or
>     contain internal power storage sufficient to flush the cache.

Right. But that is still a cache that can cause surprising results, 
although I freely admit that the caches in the disks are normally very 
reliable.

	Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol