Traditionally, Online Transaction Processing (OLTP) describes a form of transaction processing that enables a user at a terminal or workstation to update a database in real time by sending messages to an application program. More recently, OLTP has been adopted as the name of a communications protocol used by cooperating application programs processing transactions in a distributed environment.

You can view the OLTP protocol as providing a mechanism for extending traditional OLTP into client/server computing. In this modern form, transaction processing can be distributed across a number of possibly different computer systems. Tasks involved in processing a transaction can thus be shared among computers.

Client/server computing distributes processing tasks between those application programs or modules, called clients, that issue requests for services, and those application programs or modules, called servers that respond to service requests by providing the required services. A client is typically a program that interacts with users, whereas a server can be a program that interacts with the database, for instance. When a user requires a database update, the client issues an update request to the server, which does the work.

The client and server programs can reside on separate computers, thus sharing the task load and enabling machines to be configured according to the tasks they best perform.

Transaction processing can be fully distributed over a network. A number of isolated transactions on different hosts can be combined into a new global transaction, which performs multiple coordinated database updates across the network as a single unit of work. A global transaction completes or recovers as a unit, and possesses the integrity of traditional transactions, even though it might span different databases and machines.

The Unisys Open/OLTP software suite, which is built on the international standard X/ Open Distributed Transaction Processing (DTP) model, provides a basis for developing OLTP client/server applications. Agile Business Suite supports Open/OLTP on the MCP based Open/OLTP platforms.

Using interfaces to Open/OLTP, built applications can participate in an Open/OLTP environment as: