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Revision as of 17:24, 18 July 2006 (edit) 213.171.204.166 (Talk) ← Previous diff		Revision as of 13:48, 24 June 2007 (edit) (undo) Def (Talk | contribs) (changed beta to kappa. "beta" is confusing on first read. Overloaded word.) Next diff →
Line 11:		Line 11:
	> % still on alpha		> % still on alpha
-	> mnesia:add_table_copy(schema, beta@localhost, ram_copies).	+	> mnesia:add_table_copy(schema, kappa@localhost, ram_copies).
-	If beta were up and running and received a disk copy of the schema we would be done right now. However, disc-less nodes are a little special and require this extra step. Let's go ahead and start up our beta node. Obviously we need to leave the alpha node running.	+	If ''kappa'' were up and running and received a disk copy of the schema we would be done right now. However, disc-less nodes are a little special and require this extra step. Let's go ahead and start up our ''kappa'' node. Obviously we need to leave the alpha node running.
-	erl -sname beta	+	erl -sname kappa
	> mnesia:start().		> mnesia:start().
	> mnesia:info().		> mnesia:info().
Line 21:		Line 21:
	Notice that mnesia here is completely unaware that it is supposed to be a disc-less node of the system running on alpha. Here's the money line:		Notice that mnesia here is completely unaware that it is supposed to be a disc-less node of the system running on alpha. Here's the money line:
-	> % still on beta	+	> % still on kappa
	> mnesia:change_config(extra_db_nodes, [alpha@localhost]).		> mnesia:change_config(extra_db_nodes, [alpha@localhost]).
	> mnesia:info().		> mnesia:info().
-	And you should have a working disc-less node running on beta. Enjoy.	+	And you should have a working disc-less node running on ''kappa''. Enjoy.
-	Alternatively you can start up beta like this:	+	Alternatively you can start up ''kappa'' like this:
-	erl -sname beta -mnesia extra_db_nodes "[alpha@localhost]"	+	erl -sname kappa -mnesia extra_db_nodes "[alpha@localhost]"
	For more information see http://erlang.org/doc/doc-5.5/lib/mnesia-4.3.1/doc/html/Mnesia_chap5.html#5.5 .		For more information see http://erlang.org/doc/doc-5.5/lib/mnesia-4.3.1/doc/html/Mnesia_chap5.html#5.5 .

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Revision as of 13:48, 24 June 2007

Disc-less nodes are useful but require some extra steps.

First of all, we have to have a working Mnesia database with a disc_copy of a schema.

erl -sname alpha
> mnesia:create_schema([alpha@localhost]).
> mnesia:start().
> % now create some tables

Next we need to tell mnesia that the disc-less node will exist in the future. To do that we use add_table_copy on the schema.

> % still on alpha
> mnesia:add_table_copy(schema, kappa@localhost, ram_copies).

If kappa were up and running and received a disk copy of the schema we would be done right now. However, disc-less nodes are a little special and require this extra step. Let's go ahead and start up our kappa node. Obviously we need to leave the alpha node running.

erl -sname kappa
> mnesia:start().
> mnesia:info().

Notice that mnesia here is completely unaware that it is supposed to be a disc-less node of the system running on alpha. Here's the money line:

> % still on kappa
> mnesia:change_config(extra_db_nodes, [alpha@localhost]).
> mnesia:info().

And you should have a working disc-less node running on kappa. Enjoy.

Alternatively you can start up kappa like this:

erl -sname kappa -mnesia extra_db_nodes "[alpha@localhost]"

For more information see http://erlang.org/doc/doc-5.5/lib/mnesia-4.3.1/doc/html/Mnesia_chap5.html#5.5 .