Showing posts with label SSIS data flow task. Show all posts
Showing posts with label SSIS data flow task. Show all posts

Saturday, November 5, 2011

DataFlow Task Facts

Basics of Data Flow Task:

* Streaming
* Unlink control flow, multiple components can process data at the same time
* Smallest unit of the data flow is a component
* Data flows move data, but are also tasks in the control flow, as such, their success or failure effects how your control flow operates
* Data is moved and manipulated through transformations
* Data is passed between each component in the data flow
* Data flow is made up of source(s), transformations, and destinations.


Some Facts about Data Flow:

* The data flow task in SSIS (SQL Server Integration Services) sends data in series of buffers.
* This is bounded by DefaultBufferMaxRows and DefaultBufferMaxSize, two Data Flow properties.
* They have default values of 10,000 and 10,485,760 (10 MB), respectively. That means, one buffer will contain either 10,000 rows or 10 MB of data, whichever is less.
* You can adjust these two properties based on your scenario. Setting them to a higher value can boost performance, but only as long as all buffers fit in memory.
* The Data Flow task encapsulates the data flow engine that moves data between sources and destinations, and lets the user transform, clean, and modify data as it is moved.
* Addition of a Data Flow task to a package control flow makes it possible for the package to extract, transform, and load data.
* A data flow consists of at least one data flow component, but it is typically a set of connected data flow components: sources that extract data; transformations that modify, route, or summarize data; and destinations that load data. Components are connected in the data flow by paths.
* Each path specifies the two components that are the start and the end of the path. For more information, see Data Flow Elements.
* At run time, the Data Flow task builds an execution plan from the data flow, and the data flow engine executes the plan.
* We can create a Data Flow task that has no data flow, but the task executes only if it includes at least one data flow.