[erlang-questions] `mnesia:change_table_copy_type/3' issues when changing from disc to RAM

Francesco Mazzoli <>
Wed Aug 22 13:18:28 CEST 2012

Hi list,

For some reason, `mnesia:change_table_copy_type/3' fails when changing a table
replica type from ram to disc while some node containing a disc replica of the
same table is offline, with the error

  {aborted, {not_active,
             "All replicas on diskfull nodes are not active yet",

where `rabbit_user' is the table in question, and `' is the offline
node that contains a disc replica.  Note that there are other nodes with disc
replicas online.

Why does this happen?  I've looked at `mnesia_schema.erl' and it seems to do
this check (in `ensure_active/2') when the type transition (in this case disc ->
RAM) is marked as `incompatible' by `compare_storage_type/3'.

One solutions would be to delete the local replica and then re-create it, but
that's inefficient and I'm still curious on why does the problem arise in the
first place.

Francesco * Often in error, never in doubt

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