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{{Infobox software
| name                   = Oracle TimesTen In-Memory Database
| title                  = 
| logo                   = [[File:Oracle logo.svg|250px]]
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| caption                = 
| collapsible            = 
| author                 = 
| developer              = [[Oracle Corporation]]
| released               = <!-- {{Start date|YYYY|MM|DD|df=yes/no}} -->
| discontinued           = 
| latest release version = 11''g'' Release 2 (11.2.2.0)
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| status                 = Active
| genre                  = [[Relational database management system|RDBMS]]
| license                = [[Proprietary software|Proprietary]]
| website                = [http://www.oracle.com/technetwork/database/timesten/ TimesTen OTN Home Page]
}}

'''TimesTen''' is a memory-optimized, [[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.<ref name="acquisition">{{cite web|title=Oracle TimesTen Acquisition|url=http://www.oracle.com/us/corporate/Acquisitions/timesten/index.html|publisher=Oracle Corporation}}</ref> 

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]], [[IBM DB2|DB2]], [[Informix]] or[[Microsoft SQL Server|SQL Server]], whose designs must contain algorithms that attempt to minimize disk accesses.<ref>{{cite web|last=Wang|first=Wenguang|title=Storage Management in RDBMS|url=http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.138.6378|publisher=CiteSeerX}}</ref>  TimesTen provides applications with short, consistent response times and very high  throughput required by applications with  database-intensive workloads.<ref>{{cite web|title=Oracle TimesTen In-Memory Database and Oracle In-Memory Database Cache|url=http://www.oracle.com/technetwork/products/timesten/overview/index.html|publisher=Oracle Corporation}}</ref>  

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 utilize key-value pairs such as [[Memcached]] or [[Apache  Cassandra|Cassandra]], TimesTen is a full-featured relational database that can be accessed with standard APIs like [[ODBC]], [[JDBC]],  [[Oracle Call Interface|OCI]], [[Pro*C|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.<ref>{{cite web|title=Oracle In-Memory Database Cache Product Website|url=http://www.oracle.com/us/products/database/in-memory-database-cache-066510.html|publisher=Oracle Corporation}}</ref> 

TimesTen runs on most major [[Unix]]/[[Linux]] platforms and on various [[Microsoft Windows|Windows]] platforms, in  both 32-bit and 64-bit modes.<ref>{{cite web|title=TimesTen 11.2.2 Supported Platforms (from TimesTen FAQ)|url=http://www.oracle.com/technetwork/products/timesten/faq-091526.html#GENERAL6}}</ref> 

==Technical Overview==

TimesTen is an [[In-memory database| in-memory database management]] technology that provides very fast data access time. The reason TimesTen is so fast is because it was built from the ground up around the idea that all its data will reside in physical memory (RAM) during run time.<ref>{{cite web|title=Why is Oracle TimesTen In-Memory Database fast? (TimesTen 11.2.2 Documentation)|url=http://docs.oracle.com/cd/E21901_01/doc/timesten.1122/e21631/overview.htm#TTCIN120|publisher=Oracle Corporation}}</ref>  The result is very low response times, which enable high throughput, even on commodity hardware.<ref>{{cite web|title=Extreme Performance Using Oracle TimesTen In-Memory Database|url=http://www.oracle.com/technetwork/products/timesten/overview/wp-timesten-tech-132016.pdf|publisher=Oracle Corporation}}</ref> 

===Architecture and Component Overview===

====Shared Libraries====

TimesTen functionality is contained in a set of shared libraries that application developers link to their application, allowing TimesTen to execute as part of the application's process. This shared library approach is different than conventional [[Relational database management system|RDBMS]] systems where the database is essentially a set of distinct processes to which applications connect via some form of inter-process communication. This communication may take the form of a [[Client-server model|client/server]] connection spanning over a [[Computer network|network]] or it may be some form of intra-system IPC such as a Unix domain socket connection or a shared memory based connection mechanism.<ref>{{cite web|title=Shared Libraries -- Oracle In-Memory Database Cache Architecture and Components Documentation|url=http://docs.oracle.com/cd/E21901_01/doc/timesten.1122/e21631/arch.htm#BAAEBJEF}}</ref> 

====Memory-resident Database====

The data for each active TimesTen database is stored in a shared memory segment, allowing multiple TimesTen databases to be active concurrently, and also allowing an application to simultaneously access several TimesTen databases on the same system. On 64-bit platforms, the size of a TimesTen database is practically limited only by the amount of [[RAM]] available on its host computer. One customer has a production TimesTen database approaching two [[terabyte|terabytes]] in size<ref>{{cite web|title=Extreme Performance with In-Memory Database Technology – Real Life Stories -- USPS (presented at Open World 2010)|url=http://www.oracle.com/technetwork/products/timesten/overview/usps-customer-case-1446282.pdf|publisher=Oracle Corporation}}</ref> utilized for [[OLTP|on-line transaction processing]].

====Database Processes====

Starting TimesTen requires starting a background process called the TimesTen main daemon, which then starts multiple TimesTen subdaemon processes to manage each database created in the system. These subdaemon processes perform database operations such as:
# loading and unloading the database into RAM
# writing periodic fuzzy [[#Checkpoint and Transaction Log Files|checkpoints]] of the TimesTen database to disk 
# writing transaction log records from the in-memory log buffer to the [[#Checkpoint and Transaction Log Files|transaction log files]] on disk
# handling deadlocks

====Connection Modes====

Client applications that connect to traditional disk-based relational databases typically use [[Internet protocol suite|TCP/IP]] or another [[Inter-process communication|IPC]] mechanism to communicate with a database server process. In TimesTen, applications that reside in the same server as the TimesTen database can connect directly to the in-memory image of the database directly by using the TimesTen direct driver, eliminating the need for any inter-process communication of any kind, thus providing extremely fast performance.<ref>{{cite web|title=TimesTen Direct Driver Connection Overview|url=http://docs.oracle.com/cd/E21901_01/doc/timesten.1122/e21631/arch.htm#BAAGBJAC|publisher=Oracle Corporation}}</ref> If the application resides on a remote server, the application can also connect to the TimesTen database using the traditional [[Client–server model|client/server model]] of data access.

===Data Availability and Integrity===

====Checkpoint and Transaction Log Files====

All TimesTen data exists in RAM, however TimesTen does utilize non-volatile storage (such as a hard disk) for database persistence and recoverability. A TimesTen database stores all transactional data modifications in an in-memory log buffer, which is eventually persisted to disk in the form of transaction log files. In addition, TimesTen also persists snapshots of the in-memory database, called checkpoint files, to disk. The combination of checkpoint files and transaction log files allow TimesTen to provide recoverability in the event of a system failure. TimesTen implements a parallel log manager in order to maximize throughput on large SMP systems.

By default, TimesTen operates in non-durable commit mode. In this mode, a commit operation occurs purely in memory, and the writing of the log records for the transaction to disk occurs asynchronously to the commit.<ref>{{cite web|title=TimesTen Replication Overview (TimesTen 11.2.2 Documentation)|url=http://docs.oracle.com/cd/E21901_01/doc/timesten.1122/e21633/trans.htm#CIHJJHCJ|publisher=Oracle Corporation}}</ref> This provides for very low response times and very high throughput at the cost of the potential for some small amount of data loss in the event of a system failure. A true synchronous commit mode (durable commit mode) is also provided; this mode avoids the possibility of any data loss at the cost of reduced performance. When operating in synchronous commit mode, TimesTen provides automatic group commit optimization. TimesTen allows the architect / developer to balance performance versus data safety by providing control of the commit mode at three different levels: database, connection, and transaction. Another option for data protection and high-availability is to use TimesTen replication.<ref>{{cite web|title=TimesTen Replication Overview (TimesTen 11.2.2 Documentation)|url=http://docs.oracle.com/cd/E21901_01/doc/timesten.1122/e21631/availability.htm#CHDJFEHJ|publisher=Oracle Corporation}}</ref> 

====Replication====

The TimesTen replication mechanism enables you to design a [[High availability|highly available]] system by sending database updates between two or more hosts. With TimesTen replication, a ''master'' host sends updates to one or more ''subscriber'' hosts. TimesTen recommends an active-standby pair configuration for highest availability.<ref>{{cite web|title=Oracle TimesTen 11.2.2 Replication Overview|url=http://docs.oracle.com/cd/E21901_01/doc/timesten.1122/e21631/arch.htm#BAABECIB|publisher=Oracle Corporation}}</ref> An active-standby pair consists of two master databases, an ''active'' and a ''standby'' database. In addition to the active and standby databases, multiple subscriber databases can be configured to serve as disaster recovery copies or read-only farms.

Replication in TimesTen is implemented by the ''replication agent'', a daemon process that rims at every TimesTen database involved in replication. The replication agent sends and receives updates between databases by communicating with the replication agents of other databases involved in the same replication scheme. Change capture is via log-mining with in-memory optimization; under normal operating conditions change records are captured from the in-memory log buffer with no need for any disk I/O. Communication between replication agents is via an efficient stream-oriented protocol built on top of regular TCP/IP [[Internet protocol suite|TCP/IP]] connections.<ref>{{cite web|title=TimesTen Replication Configuration Overview|url=http://docs.oracle.com/cd/E21901_01/doc/timesten.1122/e21631/availability.htm#CHDJFEHJ|publisher=Oracle Database}}</ref> The replication agent is multi-threaded and in the 11.2.2 release, TimesTen supports parallel replication for increased throughput. The replication workload is automatically parallelized to maximize throughput while still maintaining correctness.<ref>{{cite web|title=TimesTen Parallel Replication Overview|url=http://docs.oracle.com/cd/E21901_01/doc/timesten.1122/e21635/setup.htm#CHDGDCFF|publisher=Oracle Database}}</ref>

===In-Memory Database Cache===

TimesTen provides the capability to cache data from an [[Oracle Database]] source. When used in this fashion,  TimesTen is referred to as ''Oracle In-Memory Database Cache (IMDB Cache)'', an Oracle Database product option.<ref>{{cite web|title=Oracle IMDB Cache Overview (TimesTen 11.2.2 Documentation)|url=http://docs.oracle.com/cd/E21901_01/doc/timesten.1122/e21631/cache.htm#CBBDAFJC|publisher=Oracle Corporation}}</ref> 

To utilize Oracle Database caching, one defines one or more SQL objects known as ''cache groups''. A ''cache group'' is a set of one or more related database tables and allows for subsets of its rows and/or columns. Database tables in a cache group must each have a defined [[Unique key|primary key]] or a unique index declared across a set of non-nullable columns and must be related in a parent-child hierarchy via [[Unique key|primary key]]-[[Foreign key|foreign key]] constraints. [[SQL]] predicates can be used to control what data is to be cached.

Once a cache group is defined, the cache group can then be "loaded", allowing Oracle Database data to be cached in TimesTen. Applications can then read from and write to cache groups, and all data modifications will then be synchronized with the corresponding Oracle database tables either automatically or manually. 

===Event Notification===

TimesTen provides an event notification mechanism through the TimesTen Transaction Log API (XLA). XLA provides functions which allow applications to be notified of data changes occurring in TimesTen tables (and also [[Data Definition Language|DDL]] occurring in the TimesTen database). XLA can also be used in conjunction with [[Materialized view|materialized views]] to simplify the process of monitoring changes made to rows spanning multiple tables. XLA works by mining the TimesTen transaction log stream in a similar manner to the replication agent.

Database application deployments that do not include an Oracle database which want to use TimesTen as an in-memory cache database can use XLA to capture updates made to the TimesTen database and, via custom application code, apply these updates to their backend database. They can also utilize a real-time data integration tool like [http://www.oracle.com/technetwork/middleware/goldengate/overview/index.html Oracle GoldenGate] to replicate changes from their backend database into TimesTen.

==History==

TimesTen was founded in [[Hewlett-Packard|HP]] labs by Marie-Anne Neimat<ref name="marie-anne">{{cite web|title=2004 Fast 50 Winner - Marie-Anne Niemat|url=http://www.fastcompany.com/fast50_04/winners/neimat.html|publisher=Fast Company}}</ref> , Sherry Listgarten, and Kurt Shoens.  In 1996, the product was spun off into a separate [[venture capital]]  funded [[Startup company|startup]] company based in [[Mountain View, California]] under the leadership of CEO Jim Groff.   The product became popular for telecommunications equipment, as response times in the [[milliseconds]] or even  [[microseconds]] were required for applications like [[Packet (information technology)|packet]] switching.  The company had  90 employees and was profitable when it was acquired by [[Oracle Corporation]] in 2005.<ref>{{cite news|title=Oracle Acquires TimesTen for Real-Time Database|url=http://www.itjungle.com/tug/tug061605-story03.html|newspaper=The Unix Guardian}}</ref>  After the acquisition, Neimat  remained as the director of TimesTen development at Oracle<ref name="marie-anne"/>, adding many Oracle database features to the product such as support for [[PL/SQL]] and integration with [[Oracle SQL Developer]] and [[Oracle Enterprise Manager]].

==Customers==

Over 1,500 companies around the globe use TimesTen for their real-time applications.<ref name="acquisition"/> TimesTen is also embedded in the [http://www.oracle.com/us/solutions/ent-performance-bi/business-intelligence/exalytics-bi-machine/overview/index.html Oracle Exalytics] appliance, released in 2012.

==References==
{{Reflist}}

==External links==
*[http://www.oracle.com/us/products/database/timesten/overview/index.html TimesTen Product Website on oracle.com]
*[http://www.oracle.com/technetwork/database/timesten TimesTen OTN website]
*[https://blogs.oracle.com/timesten/ TimesTen Blog]
*[http://www.oracle.com/technetwork/products/timesten/overview/timesten-imdb-086887.html TimesTen In-Memory Database  Overview]
*[http://www.oracle.com/technetwork/products/timesten/overview/ds-timesten-imdb-129255.pdf TimesTen In-Memory Database  Product Sheet]
*[http://www.oracle.com/us/products/database/in-memory-database-cache-066510.html Oracle In-Memory Database Cache Product Website on oracle.com]
*[http://www.oracle.com/technetwork/products/timesten/overview/timesten-imdb-cache-101293.html Oracle In-Memory Database  Cache Overview]
*[http://www.oracle.com/technetwork/products/timesten/overview/ds-imdb-cache-1470955.pdf Oracle In-Memory Database Cache  Product Sheet]
*[https://forums.oracle.com/forums/forum.jspa?forumID=244 Oracle TimesTen Community Discussion Forum]
*[http://download.oracle.com/otn_hosted_doc/timesten/1122/quickstart/html/main/home.html TimesTen 11.2.2 Quick Start Guide]
*[http://apex.oracle.com/pls/apex/f?p=44785:2:1127475523458701:FORCE_QUERY::2,CIR,RIR:P2_TAGS:TimesTen TimesTen Demos in the Oracle Learning Library]
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