In-memory database

An in-memory database (IMDB; also main memory database system or MMDB) is a database management system that primarily relies on main memory for computer data storage. It is contrasted with database management systems which employ a disk storage mechanism. Main memory databases are faster than disk-optimized databases since the internal optimization algorithms are simpler and execute fewer CPU instructions. Accessing data in memory reduces the I/O reading activity when querying the data which provides faster and more predictable performance than disk. In applications where response time is critical, such as telecommunications network equipment and mobile ads networks, main memory databases are often used.

Products

Product name	License	Description
Adaptive Server Enterprise (ASE) 15.5	Proprietary	enterprise database from Sybase)
Apache Derby	Apache License 2.0	Java RDBMS
Altibase	Proprietary	has in-memory and disk table; HYBRID DBMS
BlackRay	GNU General Public Licence (GPLv2) and BSD License
CSQL	GNU General Public Licence or proprietary
Datablitz	Proprietary	DBMS
Eloquera	Proprietary	In-memory, In-memory:persist modes
EXASolution	Proprietary	relational database management system from EXASOL), in-memory query processing, massively parallel data processing, column by column storage
eXtremeDB	commercial product	DBMS, also check out its open source PERST dbms.
Finances Without Problems	commercial product	primarily in-memory database with hybrid features
FleetDB	MIT	NOSQL db with Writing to an append-only log to provide durability.
H2	Mozilla Public License or Eclipse Public License	has a memory-only mode
HSQLDB	BSD license	has a memory-only mode
IBM TM1	Proprietary	in-memory BI and data analysis
InfoZoom	Proprietary	in-memory BI and data analysis
KDB	Proprietary	DBMS, also supports disk based data
#liveDB	Open Source	Prevalence engine
membase	Apache License	NoSQL, hybrid
Mercury	Proprietary	object oriented, in-memory data management with persistency support, in-built compiler, hosts application server on same machine; developed by staila technologies, an ETHZ spinoff
MicroStrategy		in-memory BI for MicroStrategy 9
MonetDB	MonetDB License
MySQL	GNU General Public License or proprietary	has a cluster server which uses a main-memory storage engine
Oracle Berkeley DB	Sleepycat License	can be configured to run in memory only
Panorama		for Windows and Macintosh, both single user and server versions
ParAccel	Proprietary	in-memory, columnar, relational, ACID-compliant; disk-based mode as well
Polyhedra IMDB	Proprietary	relational, supports High-Availability; acquired in 2001 by ENEA
QlikView		BI-tool developed by QlikTech
RDM Embedded	Proprietary	including hybrid
RDM Server	Proprietary	including hybrid
Redis	BSD	NoSQL Advanced key-value store with support for hashes, lists, sets, and sorted sets.
solidDB by IBM		including hybrid, HSB-based HA, Shared memory, embedded, XA, etc.
SAP HANA database	Proprietary	Database engine of the SAP In-Memory Appliance (SAP HANA) produced by SAP AG
SQLite	Public domain	hybrid, RAM and disk dbs can be used together
Starcounter		in-memory object relational dbms
Tarantool	BSD	NoSQL, extendable with Lua stored procedures
TimesTen by Oracle		in memory only or as a cache for Oracle Database
Vertipaq	Proprietary	Microsoft PowerPivot and Microsoft Analysis Services in-memory BI engine
VoltDB	GNU General Public License v3	in-memory
WebDNA	WebDNA Software Corporation	hybrid specifically designed for server-side database-driven websites - freeware
TREX		search engine in the SAP NetWeaver integrated technology platform produced by SAP AG
Xcelerix by Frontex		commercial product
WX2 by Kognitio		commercial product
Xeround		commercial product, database as a service, in-memory infrastructure with MySQL front-end