mnesia replication (Are there checksums?)

Hakan Mattsson <>
Wed Aug 31 14:25:38 CEST 2005


No, there are no table checksums. Mnesia relies on
other recovery mechanisms.

The behaviour that you call a serious bug, is
deliberate. Normally all database accesses should be
performed within transactions. If the performance is
good enough you should not use dirty access at
all. The only reason for using dirty access is to
gain better performance. But that does not come for
free, as you need to deal with almost all
concurrency issues yourself. One of these issues is
serialization of updates. If this is unexpected, the
documentation should be blamed (or possibly the
reader of the documentation ;-).

/Håkan

On Wed, 31 Aug 2005, Francesco Cesarini (Erlang Training & Consulting) wrote:

FC> I would class this as a serious bug! I have a vague recollection that
FC> there was a checksum being computed for every table, but have looked
FC> everywhere and can not find any reference for it. Maybe it was just a
FC> discussion I had with some one 10 years ago, or something... Did it ever
FC> happen?
FC> 
FC> Francesco
FC> --
FC> http://www.erlang-consulting.com
FC> 
FC> 
FC> Dan Gudmundsson wrote:
FC> > chandru writes:
FC> >  > Hi,
FC> >  >  > On 30/08/05, Serge Aleynikov <> wrote:
FC> >  > > Hello,
FC> >  > >  > > Could someone comment on the effect of short network outages
FC> > ( < 10-15
FC> >  > > s) on mnesia replication and how to prevent the inconsistency
FC> >  > > demonstrated in the example below?   I intentionally did not alter
FC> > the
FC> >  > > net_ticktime kernel parameter so that it would be greater than the
FC> >  > > duration of the brief network outage.
FC> >  >  > You can't really prevent this inconsistency if you are using
FC> > dirty
FC> >  > operations. Have you tried the same test using transactions instead
FC> > of
FC> >  > dirty operations.
FC> > 
FC> > Since dirty_operation don't grab a lock you should be able see the same
FC> > problem
FC> > with a working network ..
FC> > 
FC> > Dirty is dirty, be aware of that.
FC> > 
FC> > /Dan


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