Manufacturing Data Access is an internal interface that enables data exchange between different applications of the SAP R/3 System. Applications that have registered as services at this interface can read and write values of data points from other applications. You can subscribe to events that have occurred in other applications.

To use items (data points) of the services ODA (OPC Data Access) and OAE (OPC Alarms/Events), you must first have created a subscription in Customizing.
To do so, go to Customizing for Process Management and choose SAP ODA (OPC Data Access).

The various applications that are linked to each other through the interface are called Services. A service can be used as a client, a server, or both as a client and a server. Clients can request data from other services, while servers provide data for other services. Services that can be used both as clients and servers can provide and request data.
Furthermore, Manufacturing Data Access provides additional functions that you can use to dynamically request data points or events available as well as navigate to their maintenance environment.

Depending on whether the registered application serves as a client or a server, it can use the following functions through Manufacturing Data Access:

A client can:

• Read data points from another application
• Write data points to another application
• Subscribe to events from other applications
  When an application subscribes to events from another application, these events are automatically reported to this application when they occur. In this way, you can, for example, subscribe to value changes.
  In addition, events can contain parameters that you can read while processing an event.

A server provides:

• Data points that can be read or written by other applications
• Events to which other applications can subscribe
  Once events occur, they are published by the server.

In this way, you can:

• Synchronously read or write value of one or more data points,
  this means on request (for example, by pressing a button)
• Read or write values of one or more data points on an event-driven basis,
  this means that in running applications, data is automatically read or written – triggered by an event – without any user interaction.

Events can also be processed across different sessions.

The following services and their functions are available in the Production Planning – Process Industries (PP-PI) environment at the moment:

• MDA: Generic services
• MSG: Create process messages automatically
• PSH: PI sheets
• PMC: Manufacturing cockpits
• ODA: OPC Data Access
• OAE: OPC Alarms/Events
• SYS: System information

The service MDA is used as a server and contains the generic services BROADCAST and REDIRECT.

• You can use BROADCAST to define user-specific events. A generic data point is available for this to which you can write any value. The value change of this data point is published as an event. Other services can subscribe to this event.

• Using REDIRECT, you can address any number of data points dynamically and read or write the values belonging to them.

The transaction CO69 – Create Process Messages Automatically is a service that serves as a client. In this transaction, you can access manufacturing events and manufacturing data points using Manufacturing Data Access. You can use value help to display all events and data points available across plants:

• You can specify events as start conditions. The application thus subscribes to the event. Once it occurs, the process message is created automatically.
• You can read values from different data points and send them with the process message.

PI sheets and cockpits are services that serve both as clients and as servers.

• Reading data from another application
• Writing data to another application
• Subscribing to an event
  You can use events to subscribe to value changes.

• Events to which another application, another PI sheet, or another cockpit can subscribe.
  Example: User Logged On or Document Saved

• Global variables that other applications can access as data points

SAP ODA is a service that is used as a server. This means, it provides:

This service is used as a server and provides data points containing system information, such as Current date or User logged on. The data access to this service is defined differently by the different client applications.

The data access to the various services must be defined differently by the different client applications.

• In the transaction Create Process Messages Automatically:

• In the PI sheet and in the cockpit:

Addresses are used to access data points and events for data exchange between applications. They start with the name of the service. The remaining address parts depend on the service.

You can use the Business Add-In (BAdI) SCM_CMX_DA_SRV to register any application of the SAP R/3 System as a service.

To do so, go to Customizing for Process Management and choose Business Add-Ins in Process Management ® BAdI: Registration of a Manufacturing Data Access Service.