After completing data migration, manually migrate the configuration settings from the 11g system in to the 12c system and complete the post-migration tasks.
See Understanding Essbase Deployed in BI 12.2.1 in Oracle® Essbase Database Administrator's Guide for the procedure to migrate the following configuration settings from the 11g system to the 12c system and to complete the post-migration tasks:
- Thread Pool Configuration for Essbase
- ESSLANG Configuration Setting for Essbase Server
- Configuring Modes, Ports, and Cipher Suites
- Configuring wallets for root, Essbase Server, and Essbase clients
- Importing certificates in to the key store