Cited a posting from Oracle forum: TimesTen In-Memory Database, FYI.  

Steve,

I don't know what your product manager meant by "TimesTen can be used on top of Msft SQL Server", but I'd like to clarify a few points to help you better understand what TimesTen offers:

1. TimesTen is a relational in-memory database, and many customers use TimesTen as a standalone database for their application transactions to achieve improved response time and throughput for their database operations.

2. TimesTen has a product option where Oracle tables can be cached in TimesTen and data synchronization between the cached tables in TimesTen and the Oracle database is automatically handled by the TimesTen Cache Agent., If you use this Connect Connect to Oracle product option, the supported database is the Oracle Database.

3. There are many customers who use TimesTen in their application tier with a non-Oracle database in the backend. Typically, these applications do not require the backend database in the transactions, i.e. all transactions are handled by TimesTen (e.g. trading transactions, pre-paid account update, etc.). Now if you need to sync up with the backend database, you have a couple options:

a). Use TimesTen's Transaction Log API (XLA) to get change notifications on TimesTen transactions and then send these changes to your SQL Server datatabase. The XLA facility allows you to subscribe to changes on tables or materialized views, and the XLA subscriber receives only committed changes.

b). At the end of the day (if there is such thing for your application), do a batch updates of TimesTen data to the backend database;

c) There are some applications that need to refresh TimesTen with changes from the backend database; they either do batch updates or use the vendor provided replication facilities to send data to TimesTen.

If you have a specific application use case in mind and would like some help, I will be happy to discuss it with you offline.

Susan