Characteristics of XATMI in UPIC

This section describes the distinctive features that arise when implementing the XATMI interface in openUTM.

• All XATMI calls relevant for clients are supported. Additionally the two calls tpinit and tpterm are provided.

• Only one conversation per service is allowed.

• A maximum of 100 buffer entities can be used simultaneously within a client application. For example, with an application in C this is a maximum of 100 tpalloc calls without a tpfree call.

• The maximum message length is 32000 bytes.

  The maximum size of a typed buffer is always less than the maximum possible message length because the messages contain an “overhead” in addition to the net data. The more complex the buffer, the bigger the overhead.

  The following applies as a rule of thumb: max. buffer size = 2/3 of max. message length

  With larger data volumes, the conversational paradigm (tpsend/tprecv) should thus always be used.

• The following limits apply to name lengths:

  service name buffer name

  16 bytes 16 bytes

  In accordance with the standard, service names can be 32 bytes long; however, only the first 16 bytes are relevant (XATMI_SERVICE_NAME_LENGTH constant). It is therefore advisable to use no more than 16 bytes for service names.