OLTP stands for "online transaction processing" and refers to information systems that process transactional data. The applications generating such data often require a high volume of transactions -- such as being used concurrently by hundreds of users. An example of a commercial transaction processing application is an automated teller machine (ATM). OLTP is often contrasted with OLAP (online analytical processing) which is typically characterized by more complex queries but with much smaller volume (for example, for business intelligence reporting).