Must point out - this is not a fatal error, otherwise slapd would not have continued startup. The backend inits a new shared memory region and just starts up as normal, there's no reason to take any special action here.
Hm, back when I used back-hdb + SHM, I have to say I didn't run into this issue with OpenLDAP unless something had cleared the shared memory region (i.e., it persisted across restarts of slapd).
So while back-hdb is clearly recovering, there still seems to me to be an issue here in that short of a server reboot, the SHM segment should remain unaffected.
--Quanah -- Quanah Gibson-Mount Product Architect Symas Corporation Packaged, certified, and supported LDAP solutions powered by OpenLDAP: <http://www.symas.com>