The DTP models are composed of the following elements.

AP (Application Program)

An application program created by the system user using a high-level language. This application program is known as a UAP of OpenTP1.

Transaction Manager

Manages system transactions and supports consistency according to the update information of resources.

RM (Resource Manager)

Manages system resources such as user data.

CRM (Communication Resource Manager)

Manages resources concerning the communication between the systems.

Each element that composes a DTP model can be linked with the following interfaces.

TX interface

Instructs the start and end of a transaction from AP to Transaction Manager.

XATMI and TxRPC interfaces

Instruct the communication from AP to CRM.

XA interface

Synchronizes according to the update information of resources with Transaction Manager and RM.

XA+ interface

Extends the transaction managed by Transaction Manager to other system processing when communicating with other system using CRM.

Interface provided by RM

Instructs update of resources from AP to RM. The API to RM contains an SQL.

The following shows RMs that can be used in OpenTP1.

• RMs that manage user resources such as files
  An RM that conforms to TP1/FS/Direct Access, TP1/FS/Table Access, ISAM (ISAM/B), and X/Open
  
• RMs that manage communications by using messages
• TP1/Message Control, TP1/NET/Library, and TP1/Message Queue.

Figure 1-11 shows the relationship between the X/Open DTP model and the OpenTP1 system.

Figure 1-11 Relationship between the X/Open DTP model and the OpenTP1 system