A major difference between Transaction Processing Systems and DSS is the general purpose of each type of system. Transaction Processing Systems are designed to expedite and automate transaction processing, record keeping, and simple business reporting of transactions. Decision Support Systems are intended to assist in decision-making and decision implementation. Transaction processing is however related to the design of DSS because transaction databases often provide data for decision-oriented reporting systems and data warehouses.
Transaction Processing Systems usually provide standard reports on a periodic basis and support the operations of a company. DSS are used on demand when they are needed to support decision-making. A manager typically initiates each instance of Decision Support System use, either by using the DSS herself or by asking a staff intermediary to use a DSS. Some managers and especially clerical employees use Transaction Processing Systems to support operations. DSS are designed for use by line managers and support staff. TPS record current information and maintain a database of transaction information. Some DSS use historical internal and external data for analysis. Other DSS focus on modeling current and future scenarios and incorporate historical data, forecasts, and assumptions. TPS emphasize data integrity and consistency; and although these qualities in a system are important, a DSS places it primary emphasis on flexibility and supporting ad hoc queries and analyses.
One can draw many distinctions between Transaction Processing Systems and DSS, but analysts and managers need to stay focused on the phrase "decision support" in the term Decision Support System. Decision Support Systems are intended to improve and speed-up the processes by which people make and communicate decisions. Thus the emphasis in building a DSS is on increasing individual and organizational decision making effectiveness rather than on increasing efficiency in processing operating data.