I fixed the problem! What I did is following:
backup ldap using ldapsearch because slapcat would give you some errors when the directory is damaged Code:
ldapsearch -x -D "uid=zimbra,cn=admins,cn=zimbra" -w xxx > backup.ldif
shutdown ldap server remove all files exept DB_CONFIG from openldap-data Code:
rm -rf /opt/zimbra/openldap-data/*; touch /opt/zimbra/openldap-data/DB_CONFIG
start ldap restore backup Code:
ldapadd -x -D "uid=zimbra,cn=admins,cn=zimbra" -w xxx < backup.ldif