Oracle TimesTen vs Oracle database in-memory
There's a massive difference. TimesTen is an dedicated in-memory database.

Oracle in-memory is just an added optional extra for Oracle 12c that lets you mark data, given certain indexing rules (you drop them), as in-memory. Oracle then caches the data in memory in both a row and columnar fashion, enabling fast retrieval for both OLTP and reporting workloads. It requires no code changes for existing Oracle-based applications - completely transparent &amp; can offer significant performance improvements.