OSI/MHS Configuration and Management Manual

Sizing and Tuning Your OSI/MHS Subsystem
OSI/MHS Configuration and Management Manual—424827-003
8-3
Locations and Relationships of Message Handling
Components
implications of each network and application characteristic, in terms of sizing or
performance, vary among successive versions of OSI/MHS. Your specialist will be
better able to help you plan and tune your system if you can provide information of the
types discussed here.
Locations and Relationships of Message Handling Components
The locations and relationships among components such as MTAs and remote user
agents are important factors in defining and tuning route-selection criteria. Often it is
simplest to define routes so that a message passes through as few MTAs as possible,
but that strategy can also cause a bottleneck if an MTA is on too many routes or must
handle more traffic than its size will allow. OSI/MHS lets you define alternate routes
so that if the nearest adjacent MTA is unavailable or busy, a message can reach its
destination through another MTA.
Parallelism and Multiplexing
Along with the locations of MTAs, the amount of parallel processing in each MTA is
important and can be adjusted to improve performance. For example, you can define
multiple MR groups in the same OSI/MHS subsystem. Each MR group can send
messages to the same or different remote MTAs simultaneously; conversely, multiple
MR groups can receive messages on the same or different addresses. Thus, the
number of MR groups and the addresses assigned to them affect throughput and
tuning strategy.
Similarly, you can define multiple MS groups, each handling a subset of message-store
users, and multiple GI groups to handle the same or different gateway applications.
Characteristics like the number of X.25 lines available and the amount of multiplexing
on a given line, the number of LAN connections, and the number of controllers (or
adapters on S-series systems) used to support the same or different LANs are also
subject to tuning.
Throughput Characteristics of Adjacent MTAs
Finally, if you know the throughput characteristics of an adjacent MTA, you can use
that information to control how long an MR group will wait, after starting a transmission,
before deciding that an adjacent MTA has not received the transmission. Three
attributes determine how long OSI/MHS will wait:
•
The MR class attribute MAX-MSG-XFER-TIME specifies how many seconds the
MR group should wait for a message to transfer to the adjacent MTA. It sets the
same timer regardless of message size and must therefore be set to accommodate
the largest message to be sent. Using this attribute can be inefficient if the
message handling system supports a large range of message sizes, because the
wait time will be out of proportion for smaller messages.
•
The MTA attribute REM-MSG-THRUPUT specifies how long it takes to transfer a
message to a specific adjacent MTA. This value is a function of line speed,
adjusted to reflect the reliability of the line.