[erlang-questions] Mnesia Backup/Fallback Problems With Schema

[Chandru]

Hi Gordon,

The node name is in the schema. If you want to install_fallback on another
node, you have to change the node name in the backup file. Attached is a
module which might be of use to you. We use it quite a lot in our setup.

The code here is based on an example in the Mnesia user guide.

cheers
Chandru

On 8 June 2012 09:47, Gordon Guthrie <gordon@REDACTED> wrote:

> Folks
>
> Having some problems with mnesia backups.
>
> I have servers running with lots of tables for lots of site, so we use
> a naming convention for the tables to separate the data:
> site_1_table_1, ..., site_1_table_n
> ...
> site_m_table_1, ..., site_m_table_n
>
> I want to be able to backup individual sites and restore them - maybe
> on the original machine, maybe on another one.
>
> So I setup a checkpoint across a set of tables (site_1_table_1 to
> site_1_table_n) and back it up.
>
> The tables can be quite big so mnesia:restore/2 isn't practical and I
> have to use mnesia:install_fallback - this is where I hit problems.
>
> I get the error message:
>
>     {error,{"Cannot install fallback",
>              {"Cannot lookup",schema}}}
>
> Ok, I figured it needs the schema to be backed up as well, so I then
> build a checkpoint with the schema and the set of tables I want to
> backup. But when I run that I get a different error:
>
>     {error,{"Cannot install fallback",
>              {already_exists,'hndev@REDACTED'}}}
>
> So I am at a bit of a loss.
>
> Does install_fallback only work with whole table backups?
>
> Gordon
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