Shared Variable

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Chapter 5 General Activities Palette : Shared Variable

Shared Variable

Shared Configuration

A Shared Variable resource allows you to share data across process instances. All process instances can read and update the data stored in a shared variable.

This resource is useful if you want to marshal data across process instances or if you want to make a common set of information available to all process instances. For example, you may have a set of approval codes for incoming orders that change daily for security purposes. You can create a shared variable to hold the approval codes and create one process definition for setting the codes. You can then retrieve the shared variable in all processes that require the current approval codes.

See TIBCO ActiveMatrix BusinessWorks Process Design for more information about shared variables.

Configuration

The Configuration tab has the following fields.

Field

Global Var?

Description

Name

No

The name to appear as the label for the resource.

Description

No

Short description of the shared resource.

Persistent

Yes

The current value of the shared variable is stored in memory for fast access by process instances. However, if a process engine crashes, the current state of the shared variable may be lost. To preserve the current state of a Shared Variable resource, you can check this field to store the current value of the shared variable in the process engine’s storage location.

The current state of the shared variable is only updated in the process engine’s persistent storage when the value of the variable changes.

Multi-Engine

Yes

Checking this field specifies that you want to make the value of a Shared Variable resource available to process instances across multiple process engines.

If you choose this option, a database must be used to store process engine data. Also, only engines that are in the same deployment and use the same database to store process information can share variables. See TIBCO ActiveMatrix BusinessWorks Administration for more information on specifying a database for process engine storage during deployment. See TIBCO ActiveMatrix BusinessWorks Process Design for more information on specifying a database for process engine storage during testing.

Because multiple process engines access the shared variable when this field is checked, the current value of the variable is not stored in memory. Both retrieving the current value of the variable and assigning a new value to the variable requires I/O to the process engine’s database storage.

If this field is not checked, each process engine operates on its own set of shared variable resources. Process instances on one engine cannot retrieve the value of the shared variable set by a different process engine, when this field is unchecked.

Schema

The Schema tab allows you to define a custom schema to hold the data of the shared variable. You can define your own datatype on this tab, and you can reference an XML schema stored in the project. See Appendix A, Specifying Data Schema for a description of how to define a schema.

Initial Value

The Initial Value tab allows you to specify an initial value for the shared variable. You can choose one of the following:

•

None — specifies that no initial value is set for the shared variable. You must use the Set Shared Variable activity to set a value before you can read the value of the variable with the Get Shared Variable activity.

•

Select Value — causes the Select Value field to appear. This field allows you to choose a stored XML Instance resource containing data that matches the schema specified on the Schema tab.

•

Build Value — causes the Build Value field to appear. The Edit button brings up a smaller version of the XML Instance configuration. In this dialog you can construct an XML document that contains the initial value of the shared variable.

See TIBCO Designer Palette Reference for more information on creating XML Instance resources.

Field	Global Var?	Description
Name	No	The name to appear as the label for the resource.
Description	No	Short description of the shared resource.
Persistent	Yes	The current value of the shared variable is stored in memory for fast access by process instances. However, if a process engine crashes, the current state of the shared variable may be lost. To preserve the current state of a Shared Variable resource, you can check this field to store the current value of the shared variable in the process engine’s storage location. The current state of the shared variable is only updated in the process engine’s persistent storage when the value of the variable changes.
Multi-Engine	Yes	Checking this field specifies that you want to make the value of a Shared Variable resource available to process instances across multiple process engines. If you choose this option, a database must be used to store process engine data. Also, only engines that are in the same deployment and use the same database to store process information can share variables. See TIBCO ActiveMatrix BusinessWorks Administration for more information on specifying a database for process engine storage during deployment. See TIBCO ActiveMatrix BusinessWorks Process Design for more information on specifying a database for process engine storage during testing. Because multiple process engines access the shared variable when this field is checked, the current value of the variable is not stored in memory. Both retrieving the current value of the variable and assigning a new value to the variable requires I/O to the process engine’s database storage. If this field is not checked, each process engine operates on its own set of shared variable resources. Process instances on one engine cannot retrieve the value of the shared variable set by a different process engine, when this field is unchecked.