OLTP applications are characterized by the fact that a large number of users involved in different tasks work simultaneously and interactively with the same data and programs. This is generally controlled by a transaction monitor. Typical fields of application for OLTP applications are reservation systems, information systems and inventory management systems.
OLTP applications in BS2000 are implemented using the universal transaction monitor openUTM. openUTM is fully integrated into the operating system and, together with SESAM/SQL, forms an extremely high-performance OLTP system. Refer to the openUTM manuals and the openUTM “Concepts and Functions” manual in particular for details on openUTM.
openUTM can be seen as a sort of job processing center, where it coordinates and distributes the jobs received from the various terminals. SESAM/SQL ensures that there are no complications when a number of end users access the databases simultaneously from different processing steps. Processing is carried out in logically discrete units or transactions, which are synchronized between openUTM and SESAM/SQL. Transactions are only committed or rolled back jointly by openUTM and SESAM/SQL. A user working at a terminal knows at any time his/her precise position within a sequence of processing steps. The databases can be returned to a consistent state at any time. Refer to section "Transaction concept" for further details on the synchronization of openUTM and SESAM/SQL transactions.
The power of openUTM and SESAM/SQL is illustrated particularly vividly in large-scale installations where several thousand users are connected and several hundred transactions per second are handled. openUTM is responsible for the following important functions in OLTP applications:
openUTM ensures that response times remain short, even if large numbers of users are involved. This means that openUTM controls the processing of a large number of user requests with a small number of system tasks. This minimizes the administration overhead for the operating system.
openUTM is responsible for monitoring, controlling and handling user jobs. openUTM assigns the jobs to the corresponding programs and controls communication with the database system.
Processing is subject to transaction management, i.e. a sequence of related processing steps are executed either in their entirety or not at all.
In the event of a system crash, openUTM synchronizes with the database system and activates an automatic restart of the application and of the screen form.
SESAM/SQL and openUTM thus form an ideal basis for secure, high-performance OLTP applications.