In Designer we can specify two types of strategies:
1) Built-in strategies and
2) External strategies
With an external strategy, you can specify the exact way that objects and joins are to be extracted from the database structure. All external strategies are contained within the same text file. The name of this text file is indicated in the .prm file specific to your RDBMS. In the .prm file, the strategy file is declared as follows:
STG=[StrategyFileName] where StrategyFileName is the name of the strategy file.
An external strategy, whether for objects or for joins, is made up of the following sections:
a name and description (These are visible in the Strategies tab of the Universe Parameters dialog box.)
a type parameter: object or join
an SQL parameter or file parameter
an optional parameter that points to a connection other than the universe connection.
An external strategy can be based on SQL or a file.