Deleting mnesia tables

Sean Hinde <>
Fri Sep 6 18:16:00 CEST 2002


> >
> >The trouble is that once a live system is inconsistent it is
> >nigh on impossible to repair it without a major rebuild of at
> >least one node.
> 
> But isn't mnesia:set_master_nodes(Tab, OtherNodes) what you're
> really looking for?
> 
> It will force mnesia on the node where the call is made to
> unconditionally load Tab from one of the given nodes. The
> function can be called before mnesia is started.

It was a slightly unusual situation. We had a table mirrored across two
nodes of a 24 node system. One of these nodes was rebuilt from scratch with
a newly spliced in schema not including this table.

At some point in the past set_master_nodes had been run to set the now
'orphan' copy as the master.

The new node crashed (reason unknown) but then would not start correctly
because of an {undefined, 'orphan_table'} type error.

obviously I couldn't delete the 'orphan' because the other node wasn't
started - catch 22.

I tried setting master nodes for this table to [] but it didn't help.

I do not understand quite how, but following Hakan's procedure worked
spectatcularly well.

1. mnesia:del_table_copy(schema, ). worked

2. mnesia:delete_table(t). worked

I then started mnesia on  and it came up straight away fully
integrated into the schema with all it's tables intact. It was just as
through I had never deleted it's schema from the other nodes at all.

Quite a relief, but I've no idea quite why it worked..?

Sean



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