220 IBM Enterprise Workload Manager
9.1 Domain manager resource description
The domain manager is essentially comprised of two Java processes. The domain manager
process is responsible for aggregating data statistics from the managed servers; distributing
policies to the managed servers; and providing reporting data to the Control Center and other
potential requestors. The WebSphere Application Server process runs the EWLM Control
Center application, which provides the user interface into the domain manager. On
independent 10 second intervals, each managed server sends data statistics to the domain
manager. The size of the statistics transmitted can differ depending on the work running on
the given managed server and how it maps to the active service policy. The domain manager
keeps a live version of the aggregated statistics in memory and one hour’s worth of
one-minute summary data hardened to disk. Both the live and hardened data is utilized to
provide reporting data to the Control Center or other requestors.
Data at the managed server contains information on the specific server only, while at the
domain manager, it is aggregated to provide you with an end-to-end view of the transaction.
The domain manager reports aggregated statistical data and not single transaction response
time or behavior. If you need more detailed performance information, you will need to utilize
additional monitoring products.
9.1.1 Sizing factors
The key resources you need to size for the domain manager are CPU, memory, and disk
storage for the internal database. Following is a list of the key elements that contribute to
domain manager resource usage. The number of permutations of these elements is virtually
endless and unpredictable and depend on any given domain configuration and active policy.
In our testing we selected a subset of these that span a reasonable number of probable
environments. The elements are:
? Number of managed servers in the domain.
? Size and usage of the Service Policy in terms of number of transaction classes, process
classes, and service classes. By “usage” we mean service, transaction, and process
classes that actually have work qualified. For instance, if you have 80 transaction classes
defined, but only 10 typically utilized, then resource utilization will be much less.
? Application/Server topology in term of number of Application Environments, number of
hops, how transactions classes map to application environments/servers, and others.
The size of the service policy, combined with the level of complexity of the application/server
topology, has a larger impact on the resource requirements than does the mere number of
managed servers in the domain.
Note that the transaction rate is not a factor in the domain manager sizing.
Initial measurements were conducted to evaluate the performance and scalability of the
EWLM domain manager. This chapter contains the detailed performance results of our tests
and some general sizing recommendations based on those results. This information can be
utilized for a general appreciation of computing resources necessary to run the domain
manager.
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