Using the Data Stream Translation APIs

Using the data stream APIs, your applications can:

• Translate from a 3270 output data stream to a formatted buffer
  
• Translate from a 3270 output data stream to a 5250 data stream
• Translate from a formatted output buffer to a 5250 data stream
• Translate from a formatted input buffer to a 3270 data stream
• Translate from a 5250 input data stream to a formatted buffer
• Translate from a 5250 input data stream to a 3270 data stream
• Translate from a 5250 read screen format to a 3270 read buffer format
• Translate from a 5250 read screen with extended attributes to a 3270 read buffer format

The following figures show the translation options available when your application calls the data stream translation APIs.

Translations for Output Operations

Translations for Input Operations

When your application calls the QD0STRTS API, a translation session is opened using a user-specified device as a basis for the translation parameters. You can open as many sessions as you need, because for every session a unique translation session handle is passed back to your application.

A call to the QD0TRNDS API does the actual data stream translation using the specified parameters to indicate the type of translation. Multiple translation sessions can be active at the same time. A translation session remains open, that is the handle remains valid, until the QD0ENDTS API is called using that handle or the job that called QD0STRTS ends. The final call to the QD0ENDTS API closes or ends the translation session.

Note: If you are using the same translation parameters for many translations, you may decide to use only one QD0STRTS call for each unique set of parameters to enhance performance.

Programming Restrictions

The 5250 data streams generated by the QD0TRNDS API for your application have the following restrictions:

• Read commands are not added to the end of a data stream. Your application is responsible for sending Read modified data tag (MDT) fields to the destination display.
  
  
• If the device for which the data stream is intended does not support data in row 1, column 1 then this location is restricted from use in the input field.
  
  
• The number of input fields is dependent on the type of work station controller. The following is a list of the maximum number of input and output fields allowed per device:
  
  

  126	3270 display station
  255	5250 local display station
  126	5250 pass-through
  126	5251 display station
  230	5294 Remote Control Unit
  255	5394 Remote Control Unit
  255	5494 Remote Control Unit
  254	Client Access running work station function

  
  
• Fields that are detectable by light pens are not supported.

There are some 3270 data stream commands, orders, and attributes that are not supported. For a list of the 3270 data stream commands, orders, and attributes that are supported, see the 3270 Device Emulation Support book on the V5R1 Supplemental Manuals Web site.

All parameter values must be uppercased and left justified.