Hello,
I would strongly advise retrying with a current OpenLDAP release. Numerous sync replication bugs have been fixed since 2.4.33.
Also, to answer your earlier question, there's no such thing as "mirror mode". "mirror mode" is entirely a concept. A system either is or isn't multimaster, which delta-syncrepl works with.
See also: http://www.openldap.org/its/index.cgi/?findid=8511
Regards, Quanah
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Quanah Gibson-Mount Product Architect Symas Corporation Packaged, certified, and supported LDAP solutions powered by OpenLDAP: http://www.symas.com