Wednesday, January 28, 2009

Define simulation settings and attributes for running simulations

 
 

IBM Certification Test 992.3 - Simulation

 
 

How to Define simulation settings and attributes for running simulations

Simulation settings/attributes control the behavior of your simulation runs so that your simulation snapshots and results can be useful reflections of real-world behavior.
 
When you run a simulation, you can define the variables that you want to measure and analyze. For example, you can specify what each task will cost, how much revenue those same tasks will generate, and how long (in virtual time) a particular process will run.
 
Simulation attributes can be set at multiple levels.

Simulation preferences

At the highest level of application are the simulation preferences. Values for these attributes are set through the preferences window, and are used as default values for new simulation snapshots and profiles.
 
Simulation preferences can be set at any time, and all simulation snapshots that you create after you update the preferences will inherit those preferences.

Simulation snapshot settings 

At the next level of specificity are the simulation snapshot settings. The simulation snapshot settings present a subset of the attributes available in the preferences. The initial values for these attributes are taken from the preferences. However, you can override these values by editing the "snapshot defaults".
 
Simulation snapshot settings will override preferences. A simulation snapshot is a record of a modeling project at the single moment when the snapshot is created. When you create a simulation snapshot, simulation default values are created as part of the snapshot. When you update the default settings (located in the Defaults folder of the snapshot), all simulation profiles that you subsequently create will inherit those new attributes.

Simulation profile

More specific than the simulation snapshot settings are values inside a particular simulation profile. These settings, take their initial values from a combination of the simulation preferences and simulation snapshot settings. When you run a simulation or carry out an analysis on a simulation profile, it is the simulation profile settings that are used. Overriding the values of a specific profile affect the details of simulations you run against the profile, which will be reflected in any dynamic analyses you run against those results.
 
Process and task settings are specific to a single simulation profile, and will override both preferences and snapshot settings. You can update process and task settings of an individual simulation profile using the Attributes View.
Setting simulation attributes for activities

Setting simulation preferences

The simulation preferences define the values used to populate newly created simulation snapshots.
 
Simulation preferences provide default values to all new simulation snapshots, and their initial simulation profiles. Subsequent simulation profiles, however, take their default settings from the snapshot settings instead of referring back to the preferences. In addition, the simulation preferences are used to determine which database will be used to hold the simulation results.
 
Simulation preferences are applied across all modeling projects in your workspace. When you create a new simulation snapshot by simulating an existing process model, the values of the local simulation preferences are derived from the preferences that you have set.
You can update the following simulation preferences settings:
 
  • Setting the database connection preferences 
    Derby is provided as the default database to store simulation results, but you can also set the preferences to use a locally installed copy of IBM® DB2 Universal Database™ Express Edition if you require higher performance during simulation and analysis. 
  • Specifying general simulation preferences  
    General simulation preferences define conditions and behaviors for a process as a whole during a simulation. Attributes that you set in the simulation preferences provide default values for simulation snapshots, and their initial profiles. 
  • Setting the simulation profile label preferences  
    Set the simulation labelling preferences to create a set of default display behaviors for new simulation profiles. These preferences dictate whether labels are initially displayed in simulation profiles, and specify the content that is displayed in each label. For example, you can choose to display the associated data for repositories, and the organizations and locations for tasks. 
  • Choosing the label display behavior for new simulation profiles
    You can choose one of two sets of label preferences to use when you create new simulation profiles. You can either choose to reuse the labelling preferences that you defined for display of the process models as you edit them, or you can use your own specific simulation diagram label preferences. You can change the preferences that you are using as your default in the Simulation preferences window.
  • Setting diagram display preferences
    WebSphere Business Modeler allows you to display your simulation profile diagrams using enhanced graphics, or basic graphics.
  • Setting task simulation preferences  (General tasks  , Cost and Revenue task  )
    Task simulation attributes define conditions and behaviors for individual activities within a process during a simulation. Use the task simulation preferences to define default values for these attributes so that they are applied to all new simulation snapshots that you create.
  • Specifying token creation preferences  
    You can specify preferences for token creation settings to apply to the inputs of all new simulation snapshots you create. 
  • Setting layout preferences  
    You can specify the amount of space that the Auto-Layout option will leave between nodes in the process diagram and the simulation diagram.
Related concepts
 

 

Specifying simulation snapshot settings
The simulation snapshot settings provide default values for new simulation profiles created from that snapshot. The snapshot's own initial values, and the values of the initial profile included in the snapshot, are derived from the simulation preferences. If you make a change to the simulation snapshot settings, any profiles already created from that snapshot remain unaffected.
Related concepts
 

 

 
 

Specifying simulation profile settings

The attribute values that you set in the simulation profile are the values that are used when you carry out analysis on the profile or when you run a simulation.

 

Use these attributes to override any default values that have been inherited from the simulation snapshot settings or the simulation preferences. Modify the attributes of the top-level process to influence how the simulation runs as a while. Modify the attributes for specific activities to fine-tune the simulation to better reflect the real-world situation it models.

Note: To change the simulation attributes for internal elements of loops and subprocesses, click the Expand all icon on the main toolbar. The Simulation view displays the contents of all loops and subprocesses. You can then select elements within the expanded loop or subprocess and edit their simulation attributes.

Adding new simulation preferences

You can only define one set of simulation preferences.

Adding new simulation snapshot

You can define one or more simulation snapshots as required.

Adding new simulation profiles

You can define one or more simulation profiles as required.

 
 

Related links

 

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