See the document for the relational database management system that hosts the data warehouse.
Validate the reports as and when they are created by using the Validate Report feature in the Report Studio tools menu.
When creating expressions, before you close the editor, validate the expression by using the Validate feature.
See the Troubleshooting section in IBM Cognos® Report Studio User Guide, IBM Cognos Administration and Security Guide, and other IBM Cognos documentation.
Use the Test feature of IBM Cognos Framework Manager to verify if the data sources and query subjects are working correctly.
See the Troubleshooting section of IBM Cognos Framework Manager User Guide.
Use the Validation feature of XML Data Configuration to validate the configuration. Errors are listed in the Problems view. Look at the description and fix the errors. If, even after correcting errors, some elements in the XML Data Configuration View still have an error flag, right-click the elements, and click Validate to re-validate the element.