Online transaction processing(OLTP) database applications are optimal for managing changing data. These applications typically have many users who are performing transactions at the same time that change real-time data, in other words OLTP is a live database (accomodates inserts, deletes, updates etc)
Decision-support System (DSS) database applications are optimal for data queries that do not change data. For example, a company can periodically summarize its sales data by date, sales region, or product, and store this information in a separate database to be used for analysis by senior management. To make business decisions, users must be able to determine trends in sales quickly by querying the data based on various criteria. However, they do not have to change this data. The tables in a decision-support database are heavily indexed, and the raw data is frequently preprocessed and organized to support the various types of queries to be used. Because the users are not changing data, concurrency and atomicity issues are not a concern; the data is changed only by periodic, bulk updates made during off-hour, low-traffic times in the database.
OLTP is the online transaction processing
DSS Decision support system
This two are not same
OLTP is use for Daily transaction. DSS is use for to decide for management, etc............... http://www.geekinterview.com/Intervi...Data-Warehouse
use this link for clearly define.