Specify the server weight. The weight value you
specify controls the number of requests that are directed to the application
server. Even though you specify a value of 0 to 20 as the
weight of a server, the weight that is given to the server as a member of
a cluster is a proportion that is based on the weight assigned to the server
(the numerator) and the sum of the weights of all members of the cluster (the
denominator).
When you add a new member to a cluster, the number of requests
that are sent to each server in the cluster decreases, assuming the number
of requests coming into the cluster stays the same. Similarly when you remove
a new member from a cluster, the number of requests that are sent to each
server in the cluster increases, assuming the number of requests coming into
the cluster stays the same.
For example, if you have a cluster that consists of members
A, B, and C with weights 2, 3, and 4, respectively, 2/9 of the requests are
assigned to member A, 3/9 are assigned to member B, and 4/9 are assigned to
member C. If a new member, member D, is added to the cluster and member D
has a weight of 5, member A now gets 2/14 of the requests, member B gets 3/14
of the requests, member C gets 4/14 of the requests, and member D gets 5/14
of the requests.
![[z/OS]](../../ngzos.gif)
On the z/OS platform, weight is used to balance
some of the workload types, but others are balanced by the z/OS system.
- For HTTP requests, weights are used to distribute HTTP traffic between
the Web server plug-in and the controller handling the clustered application
server. Assign a higher weight value to the application server that should
receive the HTTP traffic.
- For Web services calls, information is transferred from a servant in
one application server to a controller in another application server. The
application server that receives the call has the highest weight value.
- Weight has no affect on Internet Inter-ORB Protocol (IIOP) requests.
IIOP requests are distributed to the correct application server using the
sysplex distributor.