Chapter 3. Optimizing Symphony file creation and distribution 41
The size of the network can help you decide whether to use a single domain or
multiple domains. If you have a small number of systems or a small number of
applications to manage with IBM Tivoli Workload Scheduler, there might not be a
need for multiple domains.
Geographic location and the communication speed between locations are one of
the primary reasons for choosing a multiple domain architecture. One domain for
each geographical location is a common configuration. If you choose a single
domain architecture, you will be more reliant on the network to maintain
continuous processing.
An IBM Tivoli Workload Scheduler network, with either a single domain or
multiple domains, gives you the ability to manage IBM Tivoli Workload Scheduler
from a single node–the master domain manager. If you want to manage multiple
locations separately, you can consider installing a separate IBM Tivoli Workload
Scheduler network at each location. Note that some degree of decentralized
management is possible in a stand-alone IBM Tivoli Workload Scheduler network
by mounting or sharing file systems.
There can be other reasons for choosing a multiple domain configuration, for
example, a domain for each building, department, business function, or
application.
The degree of interdependence between jobs is an important consideration when
designing your IBM Tivoli Workload Scheduler network. If you use multiple
domains, you should try to keep interdependent objects in the same domain.
This will decrease network traffic and take better advantage of the domain
architecture.
What level of fault-tolerance is required? An obvious disadvantage of the single
domain configuration is the reliance on a single domain manager. In a
multi-domain network, the loss of a single domain manager only affects the
agents in its own domain.
3.5.5 FTA tuning
For the test with 250,000 FTA jobs, the localopts values for the FTAs were not
changed. However, in some earlier testing (see 3.3.1, “FTA tuning parameters
(localopts)” on page 31) with a smaller number of jobs (10,000 and 50,000), the
effects of modifying the localopts parameters were tested, and a significant
improvement can be made by setting these parameters as indicated in the
following list.
42 Customizing IBM Tivoli Workload Scheduler for z/OS V8.2 to Improve Performance
Recommended localopts changes for FTAs are:
wr enable compression=yes (compress Symphony/Sinfonia if it is 4 MB or
larger)
sync level=low
mm cache enable=yes
mm cache size=512 (maximum value, unless you are running the FTA on a
low memory machine; see the following Tip about mm cache size)
bm look=9 (reduce from default value of 15 and make lower than bm read)
The following section provides more insight into these parameters.
Mailman cache (mm cache mailbox and mm cache size)
Tivoli Workload Scheduler is able to read groups of messages from the mailbox
and put them into a memory cache. Access to disk through cache is much faster
than the accessing to disk directly. The advantage is even more relevant if you
realize that a traditional mailman needs at least two disk accesses for every
mailbox message.
A special mechanism ensures that messages considered essential are not put
into cache but are immediately handled. This avoids loss of vital information in
case of a mailman failure. The settings in the localopts file regulate the behavior
of mailman cache:
mm cache mailbox: The default is no. Specify yes to enable mailman to use a
reading cache for incoming messages. Note that this option is
not used in
USS. It is
only available for UNIX and Windows systems.
mm cache size: Specify this option only if you use the mm cache mailbox
option. The default is 32 bytes and should be a reasonable value for small and
medium-sized Tivoli Workload Scheduler installations. For larger installations,
you can use the maximum value, which is 512. Higher values are ignored.
Tip: You can use larger values than 32 bytes for machines with high memory.
But if you are using the FTA on a low memory machine, be careful for not
setting this value unnecessarily large, since this would reduce the available
memory that could be allocated to other applications or other Tivoli Workload
Scheduler processes.

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