TS/MP 2.5 Release Supplement

Load Balancing PATHMON Link Requests in a Pathway Domain
The Pathway domain list in the ACSCTL file defines the percentage (weight) of link requests that
must be accepted by each PATHMON process associated with the requested domain. The weight
value of the specified PATHMONs must consider the processing capacity of the server classes that
are configured under those PATHMONs. If the weight value is not provided, it will evenly distribute
the remaining weight across all PATHMONs that do not have weight values.
Example:
%PM = \A.$PM:50, \A.$PM1, \A.$PM2
PATHMON \A.$PM is requested to fulfill 50% of the links needed to support the request load
generated for environment %PM. PATHMON \A.$PM1 and \A.$PM2 fulfills the remaining 50%
of the links evenly divided between them, at 25% each.
The algorithm that selects a link attempts to maintain the distribution as close as possible to the
weights configured. For a fully loaded system or during high load levels, the distribution of link
requests across PATHMONs is in line with the weights assigned to the PATHMONs. At low load
levels, the link usage algorithm favors links that are more responsive. Requests are processed using
the released links rather than requesting a new link. As a result, the load distribution of the links
might appear uneven at low load levels, but this does not adversely affect the response time.
The PATHMON weights in the ACSCTL file must match the server process configuration (as indicated
by the MAXSERVERS parameter) of the individual Pathway environments that form the respective
domains. Under load conditions, the ACS subsystem tries to get links proportionate to the configured
weight. If a PATHMON with a higher weight in the ACSCTL file has few server processes configured,
it will not be able to serve all the link requests received, thereby resulting in load imbalance.
Example:
Consider that the ACSCTL file on system \A has the following weights defined for domain %DOM.
%DOM = \A.$PM1:50, \A.$PM2:10, \A.$PM3:40
The PATHMONs $PM1, $PM2, and $PM3 have servers SERVER-CORRECT and SERVER-WRONG
configured. The LINKDEPTH and MAXLINKS parameter values are set to 1 for both the servers in
all the PATHMONs. The MAXSERVERS parameter values for the servers are:
$PM3$PM2$PM1PATHMON Names
Server Names
8210SERVER-CORRECT
8102SERVER-WRONG
The above configuration shows the following:
• The SERVER-CORRECT server has 50, 10, and 40 percent of processes configured in $PM1,
$PM2, and $PM3 respectively. This is how the weights have been defined for PATHMONs
$PM1, $PM2, and $PM3 for the domain %DOM in the ACSCTL file. Under load conditions,
when most links must be utilized, SERVER-CORRECT will achieve proper load balance against
the configured PATHMON weights.
• The SERVER-WRONG server has 10, 50, and 40 percent of processes configured in $PM1,
$PM2, and $PM3 respectively. During load conditions, the ACS subsystem will try to get
maximum links from $PM1. Because the number of server processes configured is not sufficient,
the links will be acquired from other PATHMONs. This results in an imbalance as compared
to the configured PATHMON weights.
Using too many dynamic server processes can distort the distribution of server links. Using the
dynamic links to service new Pathsend requests might result in an uneven link distribution, as
measured against the defined PATHMON weights.
Example:
Load Balancing PATHMON Link Requests in a Pathway Domain 25