Looks like '12.9.2.5. Example for slapd-config' section of 'Administrator's Guide' contains non-valid information. First, it is impossible to initialize hdb database with no olcSuffix attribute. Second, olcPcache attribute of oclOverlay object contains 'dbd' entry, which, I suppose, instructs slapd for using dbd back-end, while in the section below database with hdb back-end are configured.

Anyway, I haven't managed to configure proxy-cache with any type of back-ends, so I have question: is any working example exist for configuring the proxy-cache via cn=config? Any of configuration, I've managed to google in the openldap's mailists, won't work for slapd 2.4.25.