Sorry about my delay to answer you, I've been in vacation and away from PC.
I understand that I should use the same name when I'll update this file to make it easy, but it is a new installation and this reason that I need modify this entries.
I've tested your suggestion and delete operation has worked fine, but I've still had the same problem described previously when I've tried add new olcTLSCertificateFile or new olcTLSCertificateKeyFile or new olcTLSCACertificateFile. I don't understand the reason for that.
[root@localhost ldifs]# ldapmodify -Y EXTERNAL -H ldapi:/// -f 5tls.ldif
SASL/EXTERNAL authentication started
SASL username: gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth
SASL SSF: 0
modifying entry "cn=config"
ldap_modify: Other (e.g., implementation specific) error (80)