Wikipedia
TimesTen is an in-memory, relational database management system with persistence and recoverability. Originally designed and implemented at Hewlett-Packard labs in Palo Alto, California, TimesTen was spun out into a separate startup in 1996 and acquired by Oracle Corporation in 2005.
All data within a TimesTen database is located in physical memory (RAM), which means no disk I/O is required for any data operation. This is unlike traditional disk-optimized relational databases such as the Oracle Database, DB2, Informix or SQL Server, whose designs must contain algorithms that attempt to minimize disk accesses. TimesTen provides applications with short, consistent response times and very high throughput required by applications with database-intensive workloads.
As memory is far faster than hard disk, TimesTen is heavily used in applications where service level agreements require very low and predictable response times, such as telecommunication, real-time financial services trading applications, network equipment, and large web applications. Also, unlike other memory caching systems that use key-value pairs such as Memcached, Hazelcast or Coherence, TimesTen is a full-featured relational database that can be accessed with standard APIs like ODBC, JDBC, OCI, Pro*C/C++ and ODP.NET, and provides the rich functionality of the SQL query language.
Applications with existing data residing in an Oracle Database can utilize the combination of the Oracle Database and TimesTen through the Oracle In-Memory Database Cache database option, in which TimesTen functions as an in-memory cache database in front of the Oracle Database.
TimesTen runs on most major Unix/ Linux platforms and on various Windows platforms, in both 32-bit and 64-bit modes.