Working with Workflow Variables

By PenchalaRaju.Yanamala

This chapter includes the following topics:

Working with Workflow Variables OverviewPredefined Workflow VariablesUser-Defined Workflow Variables

Working with Workflow Variables Overview

You can create and use variables in a workflow to reference values and record information. For example, use a variable in a Decision task to determine whether the previous task ran properly. If it did, you can run the next task. If not, you can stop the workflow.

Use the following types of workflow variables:

Predefined workflow variables. The Workflow Manager provides predefined workflow variables for tasks within a workflow. For more information, see Predefined Workflow Variables.User-defined workflow variables. You create user-defined workflow variables when you create a workflow. For more information, see User-Defined Workflow Variables.

Use workflow variables when you configure the following types of tasks:

Assignment tasks. Use an Assignment task to assign a value to a user-defined workflow variable. For example, you can increment a user-defined counter variable by setting the variable to its current value plus 1. For more information about using workflow variables in Assignment tasks, see Working with the Assignment Task.Decision tasks. Decision tasks determine how the Integration Service runs a workflow. For example, use the Status variable to run a second session only if the first session completes successfully. For more information about using workflow variables in Decision tasks, see Working with the Decision Task.Links. Links connect each workflow task. Use workflow variables in links to create branches in the workflow. For example, after a Decision task, you can create one link to follow when the decision condition evaluates to true, and another link to follow when the decision condition evaluates to false. For more information about using workflow variables in Link tasks, see Working with Links.Timer tasks. Timer tasks specify when the Integration Service begins to run the next task in the workflow. Use a user-defined date/time variable to specify the time the Integration Service starts to run the next task. For more information about using workflow variables in Timer tasks, see Working with the Timer Task.

Use the Expression Editor to create an expression that uses variables. When you build an expression, you can select predefined variables on the Predefined tab. You can select user-defined variables on the User-Defined tab. The Functions tab contains functions that you use with workflow variables. Use the point-and-click method to enter an expression using a variable.

Use the following keywords to write expressions for user-defined and predefined workflow variables:

ANDOR NOTTRUEFALSENULL SYSDATE

Related Topics: 

Predefined Workflow Variables

Each workflow contains a set of predefined variables that you use to evaluate workflow and task conditions. Use the following types of predefined variables:

Task-specific variables. The Workflow Manager provides a set of task-specific variables for each task in the workflow. Use task-specific variables in a link condition to control the path the Integration Service takes when running the workflow. The Workflow Manager lists task-specific variables under the task name in the Expression Editor.Built-in variables. Use built-in variables in a workflow to return run-time or system information such as folder name, Integration Service Name, system date, or workflow start time. The Workflow Manager lists built-in variables under the Built-in node in the Expression Editor. For more information about built-in variables, see the PowerCenter Transformation Language Reference.

Tip: When you set the error severity level for log files to Tracing in the PowerCenter Server setup, the workflow log displays the values of workflow variables. Use this logging level for troubleshooting only.

Table 4-1 lists the task-specific workflow variables available in the Workflow Manager:

Table 4-1. Task-Specific Workflow Variables

Task-SpecificVariables

Description Task Types

Datatype

Condition Evaluation result of decision condition expression.If the task fails, the Workflow Manager keeps the condition set to null.Sample syntax:$Dec_TaskStatus.Condition = <TRUE | FALSE | NULL | any integer>

Decision Integer

EndTime Date and time the associated task ended. Precision is to the second.Sample syntax:$s_item_summary.EndTime > TO_DATE('11/10/2004 08:13:25')

All tasks Date/Time

ErrorCode Last error code for the associated task. If there is no error, the Integration Service sets ErrorCode to 0 when the task completes.Sample syntax:

All tasks Integer

$s_item_summary.ErrorCode = 24013Note: You might use this variable when a task consistently fails with this final error message.

ErrorMsg Last error message for the associated task.If there is no error, the Integration Service sets ErrorMsg to an empty string when the task completes.Sample syntax:$s_item_summary.ErrorMsg = 'PETL_24013 Session run completed with failureNote: You might use this variable when a task consistently fails with this final error message.

All tasks Nstring*

FirstErrorCode Error code for the first error message in the session.If there is no error, the Integration Service sets FirstErrorCode to 0 when the session completes.Sample syntax:$s_item_summary.FirstErrorCode = 7086

Session Integer

FirstErrorMsg First error message in the session.If there is no error, the Integration Service sets FirstErrorMsg to an empty string when the task completes.Sample syntax:$s_item_summary.FirstErrorMsg = 'TE_7086 Tscrubber: Debug info… Failed to evalWrapUp'

Session Nstring*

PrevTaskStatus Status of the previous task in the workflow that the Integration Service ran. Statuses include:- ABORTED- FAILED- STOPPED- SUCCEEDEDUse these key words when writing expressions to evaluate the status of the previous task. Sample syntax:$Dec_TaskStatus.PrevTaskStatus = FAILED

All tasks Integer

SrcFailedRows Total number of rows the Integration Service failed to read from the source.Sample syntax:$s_dist_loc.SrcFailedRows = 0

Session Integer

SrcSuccessRowsTotal number of rows successfully read from the sources.Sample syntax:$s_dist_loc.SrcSuccessRows > 2500

Session Integer

StartTime Date and time the associated task started. Precision is to the second.Sample syntax:$s_item_summary.StartTime > TO_DATE('11/10/2004 08:13:25')

All tasks Date/Time

Status Status of the previous task in the workflow. All tasks Integer

Statuses include:- ABORTED- DISABLED- FAILED- NOTSTARTED- STARTED- STOPPED- SUCCEEDEDUse these key words when writing expressions to evaluate the status of the current task. Sample syntax:$s_dist_loc.Status = SUCCEEDED

TgtFailedRows Total number of rows the Integration Service failed to write to the target.Sample syntax:$s_dist_loc.TgtFailedRows = 0

Session Integer

TgtSuccessRows Total number of rows successfully written to the targetSample syntax:$s_dist_loc.TgtSuccessRows > 0

Session Integer

TotalTransErrors Total number of transformation errors.Sample syntax:$s_dist_loc.TotalTransErrors = 5

Session Integer

* Variables of type Nstring can have a maximum length of 600 characters.

All predefined workflow variables except Status have a default value of null. The Integration Service uses the default value of null when it encounters a predefined variable from a task that has not yet run in the workflow. Therefore, expressions and link conditions that depend upon tasks not yet run are valid. The default value of Status is NOTSTARTED.

Related Topics: Evaluating Task Status in a Workflow

Using Predefined Workflow Variables in Expressions

When you use a workflow variable in an expression, the Integration Service evaluates the expression and returns True or False. If the condition evaluates to true, the Integration Service runs the next task. The Integration Service writes an entry in the workflow log similar to the following message:

INFO : LM_36506 : (1980|1040) Link [Session2 --> Session3]: condition is TRUE for the expression [$Session2.PrevTaskStatus = SUCCEEDED].

The Expression Editor displays the predefined workflow variables on the Predefined tab. The Workflow Manager groups task-specific variables by task and lists built-in variables under the Built-in node. To use a variable in an expression, double-click the variable. The Expression Editor displays task-specific variables in the Expression field in the following format:

$<TaskName>.<predefinedVariable>

2. Add a Start task and both sessions to the workflow.3. Place a Decision task after the session that updates the local orders database.Set up the decision condition to check to see if the number of workflow runs is evenly divisible by 10. Use the modulus (MOD) function to do this.4. Create an Assignment task to increment the $$WorkflowCount variable by one.

5.

Link the Decision task to the session that updates the database at headquarters when the decision condition evaluates to true. Link it to the Assignment task when the decision condition evaluates to false.

When you configure workflow variables using conditions, the session that updates the local database runs every time the workflow runs. The session that updates the database at headquarters runs every 10th time the workflow runs.

Workflow Variable Start and Current Values

Conceptually, the Integration Service holds two different values for a workflow variable during a workflow run:

Start value of a workflow variableCurrent value of a workflow variable

The start value is the value of the variable at the start of the workflow. The start value could be a value defined in the parameter file for the variable, a value saved in the repository from the previous run of the workflow, a user-defined initial value for the variable, or the default value based on the variable datatype.

The Integration Service looks for the start value of a variable in the following order:

1. Value in parameter file2. Value saved in the repository (if the variable is persistent)3. User-specified default value

4. Datatype default value

For more information about datatype default values, see Table   4-2 .

For example, you create a workflow variable in a workflow and enter a default value, but you do not define a value for the variable in a parameter file. The first time the Integration Service runs the workflow, it evaluates the start value of the variable to the user-defined default value.

If you declare the variable as persistent, the Integration Service saves the value of the variable to the repository at the end of the workflow run. The next time the workflow runs, the Integration Service evaluates the start value of the variable as the value saved in the repository.

If the variable is non-persistent, the Integration Service does not save the value of the variable. The next time the workflow runs, the Integration Service evaluates the start value of the variable as the user-specified default value.

If you want to override the value saved in the repository before running a workflow, you need to define a value for the variable in a parameter file. When you define a workflow variable in the parameter file, the Integration Service uses this value instead of the value saved in the repository or the configured initial value for the variable.

The current value is the value of the variable as the workflow progresses. When a workflow starts, the current value of a variable is the same as the start value. The value of the variable can change as the workflow progresses if you create an Assignment task that updates the value of the variable.

If the variable is persistent, the Integration Service saves the current value of the variable to the repository at the end of a successful workflow run. If the workflow fails to complete, the Integration Service does not update the value of the variable in the repository.

The Integration Service states the value saved to the repository for each workflow variable in the workflow log.

Datatype Default Values

If the Integration Service cannot determine the start value of a variable by any other means, it uses a default value for the variable based on its datatype.

Table 4-2 lists the datatype default values for user-defined workflow variables:

Table 4-2. Datatype Default Values for User-Defined Workflow Variables

Datatype Workflow Manager Default ValueDate/Time 1/1/1753 00:00:00.000000000 A.D.Double 0Integer 0Nstring Empty stringRelated Topics: Workflow Variable Start and Current Values

Creating User-Defined Workflow Variables

You can create workflow variables for a workflow in the workflow properties.

To create a workflow variable:

1. In the Workflow Designer, create a new workflow or edit an existing one.2. Select the Variables tab.3. Click Add.4. Enter the information in Table 4-3 and click OK:

Table 4-3. Options for Declaring User-Defined Workflow Variables

Field DescriptionName Variable name. The correct format is $$VariableName. Workflow

variable names are not case sensitive.Do not use a single dollar sign ($) for a user-defined workflow variable. The single dollar sign is reserved for predefined workflow variables.

Datatype Datatype of the variable. You can select from the following datatypes:- Date/Time- Double- Integer- Nstring

Persistent Whether the variable is persistent. Enable this option if you want the value of the variable retained from one execution of the workflow to the next.

Default Value

Default value of the variable. The Integration Service uses this value for the variable during sessions if you do not set a value for the variable in the parameter file and there is no value stored in the repository.Variables of type Date/Time can have the following formats:- MM/DD/RR- MM/DD/YYYY- MM/DD/RR HH24:MI- MM/DD/YYYY HH24:MI- MM/DD/RR HH24:MI:SS- MM/DD/YYYY HH24:MI:SS- MM/DD/RR HH24:MI:SS.MS- MM/DD/YYYY HH24:MI:SS.MS- MM/DD/RR HH24:MI:SS.US- MM/DD/YYYY HH24:MI:SS.US- MM/DD/RR HH24:MI:SS.NS- MM/DD/YYYY HH24:MI:SS.NSYou can use the following separators: dash (-), slash (/), backslash (\), colon (:), period (.), and space. The Integration Service ignores extra spaces. You cannot use one- or three-digit values for year or the “HH12” format for hour.Variables of type Nstring can have a maximum length of 600 characters.

Is Null Whether the default value of the variable is null. If the default value is null, enable this option.

Description Description associated with the variable.

5. To validate the default value of the new workflow variable, click the Validate button.

6. Click Apply to save the new workflow variable.7. Click OK.