Re: alock + ldbm in 2.3.21

[Quanah Gibson-Mount <quanah@stanford.edu>]

--On Wednesday, April 12, 2006 4:18 PM -0400 matthew sporleder 
<msporleder@gmail.com> wrote:

> > > Apr 11 15:21:22 labogldir02 slapd[16232]: [ID 658149 local6.debug]
> > > ldbm_back_db_open: alock package is unstable; database may be
> > > inconsistent!
> > > Apr 11 15:21:22 labogldir02 slapd[16232]: [ID 100111 local6.debug]
> > > slapd starting
> > >
> > >
> > > Can I get a status on alock for LDBM?
> > >
> > > According to:
> > > http://www.openldap.org/devel/cvsweb.cgi/servers/slapd/alock.c?hideatt
> > > ic=1&sortbydate=0
> > >
> > > it looks like ldbm is having some alock rethinks.  Should I wait for
> > > ldbm to be re-stabilized in 2.3.x?
> > >
> > alock works perfectly well with ldbm in 2.3. If you're getting that
> > message then you had an unclean shutdown. There's no rethinking of alock
> > going on, ldbm has been removed from 2.4.
>
> Sorry, could you explain this a little more?
>
> I wasn't aware that LDBM was susceptible to the same inconsistencies
> as BDB.  I thought the lack of transactions/checkpointing prevented
> this.  And if this situation did occur, I thought 2.3 was smart enough
> to try fixing itself.
>
> I did see some evidence of corruption, but I thought it was due to a
> problem with db_upgrade, or a misconfiguration.  Nevertheless, I will
> try a db_recover.
> (dn2entry_r: no entry for valid id (5) dn...)

LDBM is highly susceptible to DB corruption, that is one of the reasons it 
is being removed from OpenLDAP.  The difference between LDBM and BDB is 
that BDB will *tell* you if corruption has occurred, whereas LDBM will 
continue along merrily without giving you any type of warning.

I'd suggest reading:

<http://www.openldap.org/faq/index.cgi?_highlightWords=ldbm&file=756>


--Quanah


--
Quanah Gibson-Mount
Principal Software Developer
ITS/Shared Application Services
Stanford University
GnuPG Public Key: http://www.stanford.edu/~quanah/pgp.html