BEA's Top End TP monitor
, which it acquired from NCR enables the creation of services and applications that connect to legacy systems, multiple hardware platforms, databases, and operating systems for distributed transaction management, reliable file transfer, dynamic workload balancing, message sensitive routing, and recoverable transaction queuing.
If multiple DBMSs are accessed by a single transaction, then additional DBMS coordination is needed, often with TP monitor or OS support, via the two-phase commit protocol: To ensure all-or-nothingness despite failures, the first phase of two-phase commit requires every DBMS accessed by a transaction to put that transaction's updates on stable storage (e.g., disk).
The vendor must supply a full complement of integrated basic software, including a high-performance DBMS, communications system, and TP monitor. Application builders expect the TP monitor to offer a seamless integration of the basic software.
There are several ways to structure a TP monitor to provide these functions .
Throughout the article, it is explained why vendors choose one structure over another, using popular commercial products as examples, such as Digital's ACMS  and DECintact , IBM's CICS [11, 16, 24] and IMS/DC , and Tandem's Pathway  TP monitors. This is not an exhaustive list; most commercial computer manufacturers offer a TP monitor product.
The main function of a TP monitor is to coordinate the flow of transaction requests between terminals or other devices and application programs that can process these requests.
A TP monitor divides an application into components that perform the above steps (see Figure 1):
By decomposing the application in this manner, the TP monitor can simplify application programming by mapping these components into OS processes and by providing communications support between components.