A variable is essentially place holder that has a name, data type, scope, and value. Using variables is one of the ways where we can make a package dynamic and reusable. We ac read and changes the value of the variable within the package. Variables store values that a SSIS package and its containers, tasks, and event handlers can use at run time. The scripts in the Script task and the Script component can also use variables. The precedence constraints that sequence tasks and containers into a workflow can use variables when their constraint definitions include expressions.

Integration Services supports two types of variables:

Ø System variables

Ø User-defined variables and

System variable:

System variables are predefined variable. We can’t create and changes the values of the system variables.

For seeing the system variable, Right click on the control pane and select the variable.

Variable window will be opened

By default here we are seeing the user define variable. If you want to see the system variable the click on the grid in variable

Variable grid option window will be open and select the show system variable.

See the list of variable.

See the name space for system variable showing System and the user define variable showing User.

System variable	Data type	Description
CancelEvent	Int32	The handle to a Windows Event object that the task can signal to indicate that the task should stop running.
ContainerStartTime	DateTime	The start time of the container.
CreationDate	DateTime	The date that the package was created.
CreatorComputerName	String	The computer on which the package was created.
CreatorName	String	The name of the person who built the package.
ExecutionInstanceGUID	String	The unique identifier of the executing instance of a package.
FailedConfigurations	String	The names of package configurations that have failed.
IgnoreConfigurationsOnLoad	Boolean	Indicates whether package configurations are ignored when loading the package.
InteractiveMode	Boolean	Indicates whether the package is run in interactive mode. If a package is running in SSIS Designer, this property is set to True. If a package is running using the DTExec command prompt utility, the property is set to False.
LocaleId	Int32	The locale that the package uses.
MachineName	String	The name of the computer on which the package is running.
OfflineMode	Boolean	Indicates whether the package is in offline mode. Offline mode does not acquire connections to data sources.
PackageID	String	The unique identifier of the package.
PackageName	String	The name of the package.
StartTime	DateTime	The time that the package started to run.
ServerExecutionID	Int64	Execution ID for the package that is executed on the Integration Services server.

		The default value is zero. The value is changed only if the package is executed by ISServerExec on the Integration Services Server. When there is a child package, the value is passed from the parent package to child package.
UserName	String	The account of the user who started the package. The user name is qualified by the domain name.
VersionBuild	Int32	The package version.
VersionComment	String	Comments about the package version.
VersionGUID	String	The unique identifier of the version.
VersionMajor	Int32	The major version of the package.
VersionMinor	Int32	The minor version of the packa

User define variable:

User-defined variables are defined by package developers, and system variables are defined by Integration Services. You can create as many user-defined variables as a package requires, but you cannot create additional system variables.

We can create the user define variable as per our requirement.

Name: Name of the variable

Scope: scope of the variable.

Data type: Data type of the variable

Value: fix value

Namespace: if the variable is user define then the namespace is User if the variable is System variable then the name space is System.

Expression: we can assign the value of the variable by using expression.

If we creating the variable values variable and getting value of the variable through expression then we need to set the EvaluateAsExpression to True.