If the Novell eDirectory master replica resides on a clustered NetWare node, convert that node last in the rolling cluster conversion to OES. This also applies to a NetWare node that is running the Novell Certificate Server Certificate Authority.
For OES 2015 SP1, the replacement Linux nodes will use NetIQ eDirectory 8.8 SP8 and NetIQ Certificate Server 3.3.8. These are the same Novell products that you have used for years, but they are now maintained by NetIQ, a sister company of Novell in the Attachmate Group.