ldapsearch -h 10.14.252.104 -p 389 -D cn=admin,dc=spr -w password -s sub -a always -b dc=SPR objectClass=*Sounds like there's something wrong with your openldap build or server. Zimbra has clients with DBs of various sizes and entry counts, often in the multi-GBs, and we're not seeing any such issues.
Actually, you are doing alias deref. I believe there's a known issue with back-mdb and alias deref. Do you see the same behavior if you select -a never instead?
--Quanah -- Quanah Gibson-Mount Platform Architect Zimbra, Inc. -------------------- Zimbra :: the leader in open source messaging and collaboration