content store 
data sources
metric store
The Cognos 8 data tier contains the
content store
data sources
metric store
The content store is a relational database that contains data that Cognos 8 needs to operate, such as report specifications, published models, and the packages that contain them; connection information for data sources; information about the external namespace, and the Cognos namespace itself; and information about scheduling and bursting reports. The relational database can be Cognos Content Database or a database from a supported third-party vendor.
Design models and log files are not stored in the content store.
Cognos 8 includes the Cognos Content Database as a default content store. You can use the Cognos Content Database as your content store, or you can use other databases, such as Microsoft SQL Server, Oracle, IBM DB2, or Sybase.
The Cognos 8 service that uses the content store is named Content Manager.
Content Manager uses a JDBC (Java DataBase Connectivity) API to access the content store and metric stores. Cognos 8 comes with the JDBC drivers for Cognos Content Database and MS SQL Server. Oracle, IBM, and Sybase JDBC drivers, which are required for their respective databases, are available from their vendors.
Cognos does not publish the content store schema, but updates the schema periodically, isolating changes from the user through stable user interfaces and APIs.
Much of the information in the content store, such as report results and XML report specifications, is stored as binary large object (BLOB) fields.
PDF results are compressed from creation, to storage, to serving, to the browser. The PDF format does not allow the main body of a report to be compressed, but the page contents, fonts, and images are compressed. Adobe Acrobat Reader uncompresses PDF files at view time.
Report results in other formats, such as HTML, XML, and CSV (comma separated values), are stored in compressed form and are uncompressed by Content Manager before they are sent to a user.
Cognos Content Database is an instance of an Apache Derby database that can be optionally installed and used as the default content store. Cognos Content Database can be used where you do not want to implement a commercial database for the content store.
Apache Derby is open source software whose license terms can be found on the Apache Derby Web site (http://db.apache.org/derby/license.html). Any modifications to the Apache Derby database, and its use with other than Cognos products is not supported by Cognos. Any modifications you make to the Apache Derby database are at your own risk.
Cognos Content Database can be installed with other Cognos 8 components or installed on a separate computer. The Cognos Content Database service starts the Apache Derby database in which the Cognos Content Database is running.
If you install Cognos Content Database on the same computer as Content Manager, Cognos Content Database will be used as the default content store. For information about changing your content store, see the Installation and Configuration Guide.
Data sources, also known as query databases, are relational databases, dimensional cubes, files, or other physical data stores that can be accessed through Cognos 8. Application Tier Components use data source connections to access data sources.
Cognos 8 can be used with Enterprise Information Integration (EII) products such as the Composite Information Server.
Composite Information Server provides access to additional data sources such as LDAP, JDBC, Open XML and WSDL, and improves performance when querying data from different data sources.
In the following scenario, the EII product models a set of databases, producing a unified view as a single virtual data source. Cognos 8 accesses the EII service as though it were a single database, and the EII service joins data from the various enterprise data sources as needed.
A metric store is a relational database that contains content for metric packages. A metric store also contains Metric Studio settings, such as user preferences.
More than one metric store may be created. For example, one metric store may contain content for a sales application and another metric store may contain content for a finance application.
