Online analytical processing

Online analytical processing (OLAP) is an approach for quickly answering multi-dimensional analytical queries, and the term was coined as a modification of online transaction processing (OLTP). OLAP tools let users analyse multidimensional data interactively through three basic operations: consolidation (roll-up), drill-down, and slicing and dicing. The article states that OLAP cubes can answer complex queries in around 0.1% of the time needed for the same query on OLTP relational data, mainly through precomputed aggregations. It describes MOLAP, which stores data in multidimensional arrays, and ROLAP, which works directly with relational databases without pre-computation.