[erlang-questions] Mnesia

Dan Gudmundsson <>
Thu Oct 15 08:00:51 CEST 2015


You are right in that you are wrong, and so is the documentation then,
disc_copies tables is no longer using dets files as their backend storage.
That restriction have been removed (a long time ago).

Tough, disc_only_copies are still using dets files and have the 32bits
limit.

A pointer (or a patch) to the documentation would be nice.


On Thu, Oct 15, 2015 at 7:25 AM <> wrote:

> According to http://www.erlang.org/faq/mnesia.html
> "Dets uses 32 bit integers for file offsets,
> so the largest possible mnesia table (for now) is 4Gb".
> There is nothing there about the limits being different
> for in memory vs on disc.
> Poke around a bit more and you will find explicit claims
> that this limit applies both to disc only and to disc copies,
> e.g., "disc_copies tables are limited by their dets backend".
> You will also find the figures of 2GB and 3GB floating around.
>
> One thing that would be really nice would have to have
> accurate current limits prominently signposted (not necessarily
> *displayed*, just pointed to will do) near the beginning of the
> Mnesia manual.
>
> I've had serious problems with the Mnesia documentation in the
> past, so I'm quite prepared to believe that I have my facts
> totally wrong.
>
>
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