Streamlining Process Flow Components

Problem

You have worked hard to optimize the data and columns in your process flow, but your flow is still running too slowly.

Solution

You can try the following best practices when they are relevant to your process flows:

Work from Simple to Complex
Use Transformations for Star Schemas and Lookups
Use Surrogate Keys

Tasks

Work from Simple to Complex

When you build process flows, build by validating jobs as you build up complexity. For example, build a job subsection, and then test and validate it. Then, and then add additional components, which you can test and validate as you go. This step-by-step process of progressively building complexity into a job is supported by the following features:

the ability to test the validity of the subsections by using the options for Run From Selected Transformation, Run To Selected Transformation, and Run Selected Transformations
the ability to test each subsection by using Step and Continue to step through and validate each subsection of the entire process
the ability to verify the success of the job or its subsections by monitoring the Status, Warnings and Errors, and Statistics tabs on the Details pane of the Job Editor window
the ability to select specific transformations for inclusion in the bar chart of performance statistics on the Statistics tab

Also, consider subsetting incoming data or setting a pre-process option to limit the number of observations that are initially being processed in order to fix job errors and validate results before applying processes to large volumes of data or complex tasks. For details about limiting input to SAS Data Integration Studio jobs and transformations, see Limit Input to a Transformation.

Use Transformations for Star Schemas and Lookups

Consider using the Lookup transformation when you build process flows that require lookups such as fact table loads. The Lookup transformation is built using a fast in-memory lookup technique known as DATA step hashing that is available in SAS®9. The transformation allows for multi-column keys and has useful error handling techniques such as control over missing-value handling and the ability to set limits on errors.

When you are working with star schemas, consider using the SCD Type 2 transformation. This transformation efficiently handles change data detection and has been optimized for performance. Several change detection techniques are supported: date-based, current indicator, and version number. For details about the SCD Type 2 transformation, see About Slowly Changing Dimensions.

Use Surrogate Keys

Another technique to consider when you are building the data warehouse is to use incrementing integer surrogate keys as the main key technique in your data structures. Surrogate keys are values that are assigned sequentially as needed to populate a dimension. They are very useful because they can shield users from changes in the operational systems that might invalidate the data in a warehouse (and thereby require redesign and reloading). For example, if the operational system changes its key length or type, then a surrogate key remains valid. An operational key does not remain valid.

The SCD Type 2 transformation includes a surrogate key generator. You can also plug in your own methodology that matches your business environment to generate the keys and point the transformation to it. A Surrogate Key Generator transformation can be used to build incrementing integer surrogate keys.

Avoid character-based surrogate keys. In general, functions that are based on integer keys are more efficient because they avoid the need for subsetting or string partitioning that might be required for character-based keys. Numeric strings are also smaller in size than character strings, thereby reducing the storage required in the warehouse.

For details about surrogate keys and the SCD Type 2 transformation, see About Slowly Changing Dimensions.