[erlang-questions] Operating on remote replicas

[Ulf Wiger (TN/EAB)]

Joel Reymont wrote:
> 
> Suppose I have a node with a bunch of tables and I point 
> another node to it with extra_db_nodes. The new node will see 
> the schema of the first node but will not have local replicas 
> unless added with mnesia:add_table_copy/3.
> 
> Still, I can read from and write to these remote tables as if 
> they were local. Is this by design?

Yep.

>From the User's Guide, chapter 1.2.1 (Features):

"Table locations are transparent to the programmer.
Programs address table names and the system itself 
keeps track of table locations."

The most common way of dealing with extra_db_nodes
is to not give them local replicas, but if you want
to, you can, of course (and as far as I recall, 
AXD 301 does it sometimes.) It's not necessary in
order to access the data, but does speed up read 
access (but slows down write access due to increased
replication overhead.)

BR,
Ulf W