OSI/AS Configuration and Management Manual

Performance Considerations
OSI/AS Configuration and Management Manual—424119-001
6-3
Default Attribute Values
The operating attribute values can also cause performance problems if they are set
incorrectly or are set at non-optimum values for your system. These attribute values are
set at system generation and in the configuration. In some situations, changing an
attribute may not substantially affect performance unless the congestion of the
overcommitted resource or resources is reduced.
You must consider certain OSI-specific factors when configuring your system. Your
decisions depend, in part, on the layer at which an application process interfaces with
the OSI/AS subsystem. The functions of each layer incur certain costs in terms of
demands on system resources: the higher the layer of an application interface, the
greater the subsystem overhead.
The following subsections discuss the various OSI/AS-specific factors that you must
take into account when adjusting your configuration for better performance.
Default Attribute Values
Your OSI/AS subsystem configuration attributes define your subsystem environment.
When first setting these attributes, you specify the communications lines and the
controllers using SYSGEN or DSC procedures, and you specify the definition of
processes and subdevices using SCF.
To do an effective job when defining and setting the initial system generation and
configuration attributes, you should know and understand the following:
•
The program and system design architecture of all the application systems that use
the OSI/AS subsystem
•
OSI/AS architecture
•
The interactions of the OSI/AS subsystem with the applications and the NonStop
Kernel operating system
•
The physical layout and the attributes of the subnetwork being used
•
The meaning of the system generation program (SYSGEN) and subdevice
configuration attributes
It is also necessary to have some basic knowledge of performance analysis and tuning
concepts.
When initially configuring your subsystem, it is probably easiest to use the default
values provided by Compaq, unless other information or special requirements indicate
different values. (See Table 2-6
on page 2-26 for a list of the SERVICE object default
values set by the OSI manager process.) At the least, the default values help to get the
system up and running quickly. Then, armed with detailed knowledge about the
applications using your OSI/AS subsystem, you can monitor the system and take
corrective action as needed.
Note. Default values are not advisable for attributes such as timeouts on networks using low-
speed communications lines, or timeouts where heavy traffic volumes are anticipated. In these
cases, the attribute values should be calculated as carefully as possible.