Datasheet

connection to Resources, the DSV will not pick up the change. Where this type of caching is a huge
benefit is in development. DSVs allow you to utilize cached metadata in development, even if you’re in
an airport, disconnected. It also speeds up package development. Since your DSV is most likely a subset
of the actual data source, your SSIS connection dialog boxes will load much faster.
Precedence Constraints
Precedence constraints direct the tasks to execute in a given order. They direct the workflow of your SSIS
package based on given conditions. Precedence constraints have been enhanced dramatically in SQL
Server 2005 Integration Services conditional branching of your workflow based on conditions.
Constraint Value
Constraint values are the type of precedence constraint that you may be familiar with in SQL Server
2000. There are three types of constraint values:
❑ Success: A task that’s chained to another task with this constraint will execute only if the prior
task completes successfully.
❑ Completion: A task that’s chained to another task with this constraint will execute if the prior
task completes. Whether the prior task succeeds or fails is inconsequential.
❑ Failure: A task that’s chained to another task with this constraint will execute only if the prior
task fails to complete. This type of constraint is usually used to notify an operator of a failed
event or write bad records to an exception queue.
Conditional Expressions
The nicest improvement to precedence constraints in SSIS 2005 is the ability to dynamically follow
workflow paths based on certain conditions being met. These conditions use the new conditional expres-
sions to drive the workflow. An expression allows you to evaluate whether certain conditions have been
met before the task is executed and the path followed. The constraint evaluates only the success or failure
of the previous task to determine whether the next step will be executed. The SSIS developer can set the
conditions by using evaluation operators. Once you create a precedence constraint, you can set the
EvalOp property to any one of the following options:
❑ Constraint: This is the default setting and specifies that only the constraint will be followed in
the workflow.
❑ Expression: This option gives you the ability to write an expression (much like VB.NET) that
allows you to control the workflow based on conditions that you specify.
❑ ExpressionAndConstraint: Specifies that both the expression and the constraint must be met
before proceeding.
❑ ExpressionOrConstraint: Specifies that either the expression or the constraint can be met before
proceeding.
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Welcome to SQL Server Integration Services
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