https://bugs.openldap.org/show_bug.cgi?id=9858
--- Comment #14 from Howard Chu hyc@openldap.org --- You're going to need the mdb_drop tool, which isn't in the release. It's in ec3e4ed9d80b42743d5e87e1eba553c500334fc5
mdb_drop -s ixck
to empty the ixck DB. Looks like its contents are invalid, anyway.