What is Essbase?
Essbase is a very multidimensional database management system (MDBMS) that provides a multidimensional database platform upon which to build analytic applications. Essbase, whose name derives from "Extended Spread Sheet dataBASE", began as a product of Arbor Software, which merged with Hyperion Software in 1998. Oracle Corporation acquired Hyperion Solutions Corporation in 2007, as of 2009 it markets Essbase as "Oracle Essbase". Until late 2005 IBM also marketed the product — as DB2 OLAP Server.
The database researcher E. F. Codd coined the term "on-line analytical processing" (OLAP) in a whitepaper that set out twelve rules for analytic systems (an allusion to his earlier famous set of twelve rules defining the relational model). This whitepaper, published by Computerworld, was somewhat explicit in its reference to Essbase features, and when it was later discovered that Codd had been sponsored by Arbor Software, Computerworld withdrew the paper.
In contrast to "on-line transaction processing" (OLTP), OLAP defines a database technology optimized for processing human queries rather than transactions. The results of this orientation were that MDBMS oriented their performance requirements around a different set of benchmarks (Analytic Performance Benchmark, APB-1) than that of RDBMS (Transaction Processing Performance Council (TPC)).
Hyperion renamed many of its products in 2005, giving Essbase an official name of Hyperion System 9 BI+ Analytic Services, but the new name was largely ignored by practitioners. The Essbase brand was later returned to the official product name for marketing purposes, but the server software still carried the "Analytic Services" title until it was incorporated into Oracle's Business Intelligence product suite. 
In August 2005, Information Age magazine named Essbase as one of the 10 most influential technology innovations of the previous 10 years, along with Netscape, the BlackBerry, Google, virtualization, Voice Over IP (VOIP), Linux, XML, the Pentium processor and ADSL. Editor Kenny MacIver said: "Hyperion Essbase was the multi-dimensional database technology that put online analytical processing on the business intelligence map. It has spurred the creation of scores of rival OLAP products – and billions of OLAP cubes".