Governor Settings in Cognos:

Governor settings are used to reduce system resource requirements and improve performance. You set governors before you create packages to ensure the metadata in the package contains the specified limits. All packages that are subsequently published will use the new settings. There are a number of governors that you can set. Governor settings in the model can be overridden by governor settings in Report Studio

For Example,

Report Table Limits - You can control the number of tables that a user can retrieve in a query or report

Data Retrieval Limits - You can control the number of rows that are returned in a query or report

Query Execution Time Limits - You can limit the time that a query can take 

Large Text Items Limit - You can control the character length of BLOBS (binary large objects) that a user can retrieve in a query or report

Allow Enhanced Model Portability at Run Time - You can use a separate but structurally similar data source at run time. The database schema must be the same between the two data sources.

Allows Usage of Local Cache - Select this governor to specify that all reports based on this model should use cached data.

Outer Joins - You can control whether outer joins can be used in your  query or report.

Cross-Product Joins - You can control whether cross-product joins can be used in your query or report.

Use With Clause When Generating SQL - You can choose to use the With clause with Cognos SQL if your data source supports the With clause.

Suppress Null Values for Dimensional Data Sources - This governor is supported for SAP BW data sources only. It does not work with relational or OLAP data sources.