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About DAC Repository Objects

The DAC repository stores application objects in a hierarchical framework that defines a data warehouse application.

A data warehouse application comprises the following repository objects:

• Tables. Physical database tables defined in the database schema. Can be transactional database tables or data warehouse tables. Table types can be fact, dimension, hierarchy, aggregate, and so on.
• Table group. A logical grouping of tables that defines a logical relationship between its component tables. The table group definition is based on a central or a main table that drives the relationship between itself and the other tables in the group. For example, table groups can be star schemas based on a central fact and its dimensions and aggregates.
• Subject area. A logical grouping of table groups that is related to a particular subject or application context. The subject area derives its component tables indirectly from the table group. Subject Area definitions are used for scheduling. A subject area or set of subject areas can be scheduled for full or incremental loads on a single time schedule.
• Execution plan. A data transformation plan defined on subject areas that need to be transformed at certain frequencies of time. An execution plan is defined based on business requirements for when the data warehouse needs to be loaded. Execution plans are scheduled in sequence, not in parallel.
• Task. A Task can be related to data transformation or database objects. Tasks typically operate on a set of database tables, but they can be independent of the database, for example, creating a file or executing an OS command. Tasks can be of different types, such as extract, load, or batch script, and so on, and can be classified as pre-ETL or post-ETL.
• Dependency Rule. A rule that determines the order in which tasks are executed. Dependency rules are defined to determine the sequence of when tasks can run, ensuring that data consistency is maintained for the warehouse. Dependency rules are defined at the task level.
• Schedule. A schedule specifies when and how often an execution plan runs. An execution plan can be scheduled for different frequencies or recurrences by defining multiple schedules.

Figure 5 shows the hierarchical relationship among the repository objects.

Figure 5.  DAC Object Hierarchy