OSI/FTAM Programming Guide

Using FTM Procedure Calls
HP NonStop OSI/FTAM Programming Guide—528612-001
4-15
Grouping Control
Grouping Control
Grouping control allows your application to perform a series of confirmed services as
one interaction between the initiator and responder.
The request primitives for these services are bracketed with the F-BEGIN-GROUP and
F-END-GROUP request primitives. The FTAM initiator concatenates the grouped
FTAM primitives and sends them in a single request PDU. The responder processes
the PDU and retains its response to each of the requests until the group is complete or
until a state failure occurs. The responder then returns its responses as a single
response PDU. If the grouped request fails, the state of the FTAM association is the
same as it was just before the attempt to run the failed request.
The transfer, management, and transfer-and-management service classes require that
you group primitives. Grouping is optional for the file-access service class. In general,
grouping improves throughput, but you should not use grouping (where optional) if your
application performs conditional handling based on the outcome of requests within a
sequence. Figure 4-1 shows an example of grouping the select and open services as a
single grouped service.
As only two actual data transfers occur between the initiator and responder (the
grouped request followed by the grouped response), grouped services generally take
less elapsed time than their non-grouped counterparts.
To use grouping control, you must negotiate the grouping functional unit in the
F-INITIALIZE service. Additionally, grouping control is limited to the five basic grouped
sequences shown in Table 4-6 on page 4-16, depending on the service class
negotiated. Services in square brackets are optional within the sequence. The vertical
Figure 4-1. Grouped Select and Open Services
VST0401.vsd
F-BEGIN-GROUP request
F-SELECT request
F-OPEN request
F-END-GROUP request
F-BEGIN-GROUP confirm
F-SELECT confirm
F-OPEN confirm
F-END-GROUP confirm
F-BEGIN-GROUP indication
F-SELECT indication
F-OPEN indication
F-END-GROUP indication
F-BEGIN-GROUP response
F-SELECT response
F-OPEN response
F-END-GROUP response
Grouped Service
Initiating Process Responding Process