Maximum Number of Report Tables

You can control the number of tables that a user can retrieve in a query or report. When a table is retrieved, it is counted each time it appears in the query or report. The limit is not the number of unique tables. If the query or report exceeds the limit set for the number of tables, an error message appears and the query or report is shown with no data.

A setting of zero (0) means no limit is set.

Maximum Number of Retrieved Rows

You can set data retrieval limits by controlling the number of rows that are returned in a query or report. Rows are counted as they are retrieved.

When you run a report and the data retrieval limit is exceeded, an error message appears and the query or report is shown with no data.

You can also use this governor to set limits to the data retrieved in a query subject test or the report design mode.

A setting of zero (0) means no limit is set.

Query Execution Time Limits

You can limit the time that a query can take. An error message appears when the preset number of seconds is reached.

A setting of zero (0) means no limit is set.

Large Text Item Limit

You can control the character length of BLOBS (binary large objects) that a user can retrieve in a query or report. When the character length of the BLOB exceeds the set limit, an error message appears, and the query or report is shown with no data.

A setting of zero (0) means no limit is set.

Outer Joins

You can control whether outer joins can be used in your query or report. An outer join retrieves all rows in one table, even if there is no matching row in another table. This type of join can produce very large, resource-intensive queries and reports.

Governors are set to deny outer joins by default. For example, outer joins are not automatically generated when you test a query item in Framework Manager.

SQL is generated automatically when you

Cross-Product Joins

You can control whether cross-product joins can be used in your query or report. A cross-product join retrieves data from tables without joins. This type of join can take a long time to retrieve data.

The default value for this governor is Deny. Select Allow to allow cross-product joins.

Shortcut Processing

You can control how shortcuts are processed by Cognos 8.

When you open a model from a previous release, the Shortcut Processing governor is set to Automatic. Automatic is a shortcut that exists in the same folder as its target and behaves as an alias, or independent instance. However, a shortcut existing elsewhere in the model behaves as a reference to the original. When you create a new model, the Shortcut Processing governor is always set to Explicit.

If you set the governor to Explicit, the shortcut behavior is taken from the Treat As property. If the Shortcut Processing governor is set to Automatic, we recommend that you verify the model and, when repairing, change the governor to Explicit. This changes all shortcuts to the correct value from the Treat As property based on the rules followed by the Automatic setting.

The Shortcut Processing governor takes priority over the Treat As property. For example, if the governor is set to Automatic, the behavior of the shortcut is determined by the location of the shortcut relative to its target regardless of the setting of the Treat As property is.

SQL Join Syntax

You can control how SQL is generated for inner joins in a model by selecting one of the following settings:

• The Server determined setting uses the UseSQL99JoinSyntax entry in the CQEConfig.xml file to determine the syntax. If there is not a UseSQL99JoinSyntax entry in the CQEConfig.xml file, then the Implicit setting is used. Server determined is the default value for this governor.

• The Implicit setting uses the where clause.

  For example,

  SELECT publishers.name, publishers.id,
  books.title FROM publishers, books WHERE publishers.id
  = books.publisher_id ORDER BY publishers.name, books.title;

• The Explicit setting uses the from clause with the keywords inner join in an on predicate.

  For example,

  SELECT
  publishers.name, publishers.id,
  books.title FROM publishers INNER JOIN books ON publishers.id
  = books.publisher_id ORDER BY publishers.name, books.title;

You can set the join type on the query property in Report Studio to override the value of this governor.

Regardless of the setting you use for this governor, the Explicit setting is used for left outer joins, right outer joins, and full outer joins.

This governor has no impact on typed-in SQL.

Allow Enhanced Model Portability at Run Time

This governor is selected upon initial upgrade of a Cognos ReportNet 1.x model. It prevents rigid enforcement of data types so that a Cognos 8 model can function as a ReportNet 1.x model until you update the data types in the metadata. After you have verified that the model has been upgraded successfully, clear this governor.

Other than for initial upgrade, there are limited uses for this governor. For example, you have created a model for use with a data source and you want to run it against a different data source. The new data source must be structurally similar to the original data source, and the database schema must be the same between the two data sources. If you select this governor, Cognos 8 retrieves metadata from the data source and caches it instead of using the metadata already cached in the model. When you have completed modifying and testing the model against the new data source, clear this governor.

If you do not use this governor, you must ensure that the following metadata is the same in the original and new data sources:

• collation sequence name

• collation level

• character set

• nullability

• precision

• scale

• column length

• data type

Allow Usage of Local Cache

Select this governor to specify that all reports based on this model will use cached data. For a new model, this governor is enabled by default.

Allow Dynamic Generation of Dimension Information

This governor is selected only upon initial upgrade of a ReportNet 1.x model. This governor allows consistent behavior with ReportNet 1.x by deriving a form of dimension information from the relationships, key information, and index information in the data source.

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.

The With clause is turned on for models created in Cognos 8. For upgraded models, it is turned off unless it was explicitly turned on in the ReportNet model prior to upgrading.

Suppress Null Values for SAP BW Data Sources

This governor is supported for SAP BW data sources only. It does not work with relational or OLAP data sources.

Some queries can be very large because null values are not filtered out. Null suppression removes a row or column for which all of the values in the row or column are null (empty). Null suppression is performed by SAP BW. This reduces the amount of data transferred to the Cognos 8 client products and improves performance.

The default value for this governor is to suppress null values. If you clear this governor, null values are not suppressed for any report or analysis in Cognos 8.

There is a property called Suppress in Report Studio that overrides this governor. If the Suppress property is set to None, null values are included in the result set even if the governor is set to suppress null values.

Query Reuse in Cognos Viewer

If you want a report to use a different setting than the model, you can do this in Report Studio. In the Properties pane, change the Use Local Cache property. Set the property to No if you want to always execute the query. Set the property to Yes if you want to use cached results. If you want the report to use the same setting as the model, change the setting to Default.

Changing the Use Local Cache property for one report does not affect other reports.

Reusing Cached Data in Query Studio

Query Studio reuses cached data under various conditions. If query reuse is turned on in the model and the action can be satisfied by a subset of the cached data set, the report uses the cached data. For example, changes to the report such as adding a filter or removing a column, may change the report data, but the request can still be satisfied from a subset of the cached data.

If query reuse is turned off and the action can be satisfied from the cached data set without modifications, the report still uses the cached data. For example, changing the report format uses the previous data set even if query reuse is turned off. This is known as cursor reuse. Cursor reuse is used when the cached data can satisfy the request without modifications.

Reports that were created in Query Studio always use the same setting as that specified in the model. If the model has query reuse turned on, the report attempts to use the cached data.

Deciding Whether to Use Query Reuse in Your Environment

Before deciding whether or not to turn query reuse on, consider the following:

• If most report consumers run reports interactively but run them only once, you may not experience a high level of performance improvement by caching data.

  Note: Regardless of the query reuse settings, reports that run in batch mode do not cache data.

• The size of the cache may impact Cognos 8 scalability. For example, if a report has a large result set, the cache will also be large. This should be taken into account when sizing and configuring your server environment.

Impact of Overriding the Quality of Service Indicator

Framework Manager determines the quality of service for functions based upon the data source type. Taking into consideration the context of the model, you can override the quality of service that is determined by the product. Overriding the quality of service provides guidance to your users. It does not change the level of support for that function in your data source.

When a package is made by combining sub-packages, quality of service overrides in the parent package take precedence. If there is no parent override, the quality of service for the child packages are aggregated as described above.

Consider Your Users

Ultimately, the goal is to provide your users with enough information to satisfy their business requirements, but not enough to confuse them. If your users are unable to make decisions regarding which functions to use based on the quality of service indicators, you should consider publishing separate packages for different groups of users. If your users require access to functions whose quality of service is less than Unconstrained, you should document the restrictions of those functions when you set the quality of service.

Impacts on Performance

The quality of service indicators has no direct impact on query performance. Service indicators are intended to give you some control over which functions are available for use. You can then prevent your users from using functions that could result in long running queries or queries that fail.

It is important to note that if you use functions that are not available in your data source, Framework Manager tries to compensate by using local processing on the report server. This may have an impact on query performance because the work is done on your report server instead of on your data source server.

In some situations, local processing may require more data to be retrieved from the data source server, which has an impact on both the data source server and the network. For example, OLAP functions are not available in a relational data source. If you attempt to use OLAP functions with a relational data source, Framework Manager uses the dimensional information in the data source to generate a local cube and run the OLAP functions against the cube. This requires retrieval of dimensional information from the data source server and extra processing on the report server.