Informatica Data Warehousing

You should configure the mapping with the least number of transformations and expressions to do the most amount of work possible. You should minimize the amount of data moved by deleting unnecessary links between transformations.

For transformations that use data cache (such as Aggregator, Joiner, Rank, and Lookup transformations), limit connected input/output or output ports. Limiting the number of connected input/output or output ports reduces the amount of data the transformations store in the data cache.

You can also perform the following tasks to optimize the mapping:

Configure single-pass reading.

Optimize datatype conversions.

Eliminate transformation errors.

Optimize transformations.

Optimize expressions. You should configure the mapping with the least number of transformations and expressions to do the most amount of work possible. You should minimize the amount of data moved by deleting unnecessary links between transformations.

For transformations that use data cache (such as Aggregator, Joiner, Rank, and Lookup transformations), limit connected input/output or output ports. Limiting the number of connected input/output or output ports reduces the amount of data the transformations store in the data cache.

Its a session option. when the informatica server performs incremental aggr. it passes new source data through the mapping and uses historical chache data to perform new aggregation caluculations incrementaly. for performance we will use it.

When using incremental aggregation, you apply captured changes in the source to aggregate calculations in a session. If the source changes incrementally and you can capture changes, you can configure the session to process those changes. This allows the Integration Service to update the target incrementally, rather than forcing it to process the entire source and recalculate the same data each time you run the session.

For example, you might have a session using a source that receives new data every day. You can capture those incremental changes because you have added a filter condition to the mapping that removes pre-existing data from the flow of data. You then enable incremental aggregation.

When the session runs with incremental aggregation enabled for the first time on March 1, you use the entire source. This allows the Integration Service to read and store the necessary aggregate data. On March 2, when you run the session again, you filter out all the records except those time-stamped March 2. The Integration Service then processes the new data and updates the target accordingly.

Consider using incremental aggregation in the following circumstances:

You can capture new source data. Use incremental aggregation when you can capture new source data each time you run the session. Use a Stored Procedure or Filter transformation to process new data.

Incremental changes do not significantly change the target. Use incremental aggregation when the changes do not significantly change the target. If processing the incrementally changed source alters more than half the existing target, the session may not benefit from using incremental aggregation. In this case, drop the table and recreate the target with complete source data.

Note: Do not use incremental aggregation if the mapping contains percentile or median functions. The Integration Service uses system memory to process these functions in addition to the cache memory you configure in the session properties. As a result, the Integration Service does not store incremental aggregation values for percentile and median functions in disk caches.

Standalone repository. A repository that functions individually, unrelated and unconnected to other repositories.

Global repository. (PowerCenter only.) The centralized repository in a domain, a group of connected repositories. Each domain can contain one global repository. The global repository can contain common objects to be shared throughout the domain through global shortcuts.

Local repository. (PowerCenter only.) A repository within a domain that is not the global repository. Each local repository in the domain can connect to the global repository and use objects in its shared folders.

Power Center repository is used to store informatica's meta data .

Information such as mapping name,location,target definitions,source definitions,transformation and flow is stored as meta data in the repository.

Source definitions. Definitions of database objects (tables, views, synonyms) or files that provide source data.

Target definitions. Definitions of database objects or files that contain the target data.

Multi-dimensional metadata. Target definitions that are configured as cubes and dimensions.

Mappings. A set of source and target definitions along with transformations containing business logic that you build into the transformation. These are the instructions that the Informatica Server uses to transform and move data.

Reusable transformations. Transformations that you can use in multiple mappings.

Mapplets. A set of transformations that you can use in multiple mappings.

Sessions and workflows. Sessions and workflows store information about how and when the Informatica Server moves data. A workflow is a set of instructions that describes how and when to run tasks related to extracting, transforming, and loading data. A session is a type of task that you can put in a workflow. Each session corresponds to a single mapping.