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IBM Tivoli Identity Manager Performance Tuning Guide
Page 5
2 IBM WebSphere Application Server
Regardless of the installation type (single server or cluster), the IBM Tivoli Identity Manager server can be
thought of as two components: WebSphere Application Server (the J2EE application server running the
application) and the IBM Tivoli Identity Manager application itself. Both components need to be tuned.
WebSphere Application Server allows you to use a variety of settings to tune your environment. This
document discusses the timeouts and Java Messaging Service (JMS) queue endpoints.
2.1 Java virtual machine (JVM) size
By default, WebSphere Application Server sets the maximum JVM size to 256 MB. This value is too small
for the IBM Tivoli Identity Manager product to run beyond a basic concept test and should be increased to
a minimum of 768 MB. If your server has adequate available RAM increase this value to as much as 1.5
GB. For large reconciliations or role and policy evaluations, the default values will not be enough memory
to complete these tasks.
The maximum JVM size is not the actual maximum allocated size of the Java heap – as much as 15% is
allocated to a portion of the heap for the system’s use. IBM recommends that you not use a value higher
than 1.5 GB even if your system has the available memory.
Do not set the JVM heap size to be larger than the physical RAM. The WebSphere Application Server
suffers significant performance degradation if the operating system swaps out the JVM to swap space.
Consequences of this include very slow user interface (UI) performance, transaction roll backs, timeouts,
and high disk utilization.
Determining the values
initial_jvm_heap_size – The initial size of the JVM heap in megabytes. Recommended value:
256 MB.
max_jvm_heap_size – The maximum size of the JVM heap in megabytes. Recommended value:
768 MB.
Setting the values
1) Open the Administration Console.
2) Expand the Servers list in the navigation pane.
3) Select Application Servers in the navigation pane.
4) Select the server to manage.
5) Select Process Definition from the Additional Properties pane at the bottom.
6) Select Java Virtual Machine from the Additional Properties pane at the bottom.
7) Set the Initial Heap Size to initial_jvm_heap_size.
8) Set the Maximum Heap Size to max_jvm_heap_size.
9) Repeat this procedure for each IBM Tivoli Identity Manager server.
Stop and restart each Application Server for these changes to take effect.
2.2 Workload management (WLM) timeout
The WebSphere Application Server on z/OS provides a timeout value for how long it should wait for IIOP
requests to complete. WebSphere Application Server uses the workload management (WLM) timeout
value to terminate hung threads thereby preventing the hung thread from holding onto resources needed