Basic and Mapped Conversations Compared

The following table offers some guidelines for choosing between basic and mapped conversations for your TPs. For definitions of basic and mapped conversations, see Fundamental Terms for TPs and LUs.

Characteristic Basic conversations Mapped conversations
Common use Generally used for service TPs. Generally used for application TPs.

Partnering Must be used to communicate with an existing TP that uses basic verbs. Must be used to communicate with an existing TP that uses mapped verbs.

Sending and receiving method Before a TP can begin a send operation, it must convert data records into logical records. The TP does this by adding a 2-byte prefix that indicates the length of the record. A TP can send several logical records at one time.

When a partner TP receives logical records, it must reconstruct them into usable data records. For more information, see Logical Records Used in Basic Conversations.

A TP sends data one record at a time. Neither the sending TP nor the receiving TP needs to convert data records between different forms.
Abnormal termination In the DEALLOCATE verb, a TP can indicate whether an error or ABEND (abnormal program termination) was caused by a TP or by a program using the TP. A TP can indicate an error or ABEND, but cannot tell whether a problem was caused by a TP or by a program using a TP.
A TP can indicate whether an ABEND was caused by a timeout or by a critical error.

A TP cannot indicate the cause of an ABEND.
Error logging For an error or ABEND, a TP can send an error message, in the form of a general data stream (GDS) error log variable, to the local log and to the partner LU. For an error or ABEND, a TP cannot send an error message to the local log or to the partner LU.