See Post-Migration Procedure
in the OES 2018 SP2: Migration Tool Administration Guide.
Use iManager or the Java Management Console to check for the existence of the following objects:
DNS-DHCP
DNSDHCP-GROUP
RootServerInfo
DNS Server object
Use the Clusters plug-in for iManager to verify the Cluster load script and unload script of the DNS cluster resources.
See DNS Load, Unload, and Monitor Scripts
in the OES 2018 SP2: DNS/DHCP Services for Linux Administration Guide.
Start the DNS server on the OES cluster.