Online Analytical Processing (OLAP) means analyzing large quantities of data in real-time.
Unlike Online Transaction Processing (OLTP), where typical operations read and modify individual and small numbers of records, OLAP deals with data in bulk, and operations are generally read-only.
The term OLTP is created by E. F. Codd in the 1980s. He proposed 12 criteria to define an OLTP database system. The term OLAP and criteria were widely accepted as the standard by vendors and the users to evaulate the database system.
In 1990s, he came up the term OLAP and again proposed 12 criteria to define the database system that facilitates the analytics services in real-time.
Some use OLAP and data warehousing interchangeably. Usually, however, OLAP is referring to the tool or the software system that organizes the data warhouse and makes the data easily accessible.
Definition from Oracle:
OLAP functionality is characterized by dynamic, multidimensional analysis of historical data, which supports activities such as the following:
- Calculating across dimensions and through hierarchies
- Analyzing trends
- Drilling up and down through hierarchies
- Rotating to change the dimensional orientation
OLAP tools can run against a multidimensional database or interact directly with a relational database.
– From Oracle Database Data Warehousing Guide 10g R2