OSI/FTAM Programming Guide

ISO FTAM Concepts
HP NonStop OSI/FTAM Programming Guide—528612-001
2-18
Service Class Constraints
Service Class Constraints
The FTAM regimes constrain, or limit, the order in which you can invoke FTAM
services. This subsection describes further constraints that also apply to the various
service classes. Because many of the constraints involve grouped services, the
concept of grouping services is described first.
Grouping of Services
Many of the FTAM services addressed in this subsection are grouped services. The
grouping of services allows a number of regimes to be established or released in a
single interaction. For grouped services, the initiating system brackets the group of
requests with the grouping control primitives F-BEGIN-GROUP and F-END-GROUP.
The responding system processes and retains its response to the individual requests
until the group of actions is complete, or until it detects a state-result failure, that is, a
failure to establish the requested regime.
Grouping improves throughput because the whole grouped request crosses the
network as a single PDU.
When specifying grouped requests, you must consider the value of the threshold
parameter of F-BEGIN-GROUP. The threshold parameter specifies the number of
primitives that must be successfully completed before any part of the group can
succeed. Generally, a primitive is categorized as successful or unsuccessful on the
basis of its state-result parameter. Primitives that have no state-result
parameter are considered successful for the purposes of the threshold count.
Checkpointing
Cancel data
transfer
(for
recoverable
errors)
Key:
M indicates that the functional unit is mandatory for the given service class.
O indicates that the functional unit can be used optionally with the given service class.
* indicates that either read or write—or both—is mandatory.
** indicates that the functional unit is not permitted with this service class.
Note. NonStop FTAM does not support the FADU-locking, recovery, and restart-data-transfer
functional units.
Table 2-4. Relationship of Functional Units to Services and Service
Classes (page 3 of 3)
Service Classes
Functional
Units Services
File
Transfer
File
Access
File
Management
File Transfer
and
Management
Unconstr-
ained