Version controlling
Cognos allows direct connection to certain version controlling software (Visual Source Safe being the most popular) for Framework Manager. However, there is no direct mechanism for reports.
The following methods are seen in different organizations for version controlling of reports:
Copy the report specification to the clipboard, save it as an XML file, and store it in the version controlling system. This method allows easy comparison to prior versions of the report, and hence is good for code review during any changes. However, it can be tedious. Also, restoring to an older version needs to be done for one report at a time. This also breaks any existing report views defined at the target location.
Export the whole suite of reports and store the export file (the ZIP format) in the version controlling system. This is less tedious compared to the previous one as only one file is created for the whole suite of reports. Reverting to an older and stable state is easy (the entire suite is reverted so that you can bring the system back to older and stable state, like baseline). However, this method is not particularly useful while troubleshooting a report to check what changed in it over the versions.
Use third-party tools. It is possible to hook up to the content store to retrieve the information. There are some third-party tools available that use this method to retrieve report specifications and do certain jobs. You can consider the tools like MotioCI to automatically record report versions and track changes. They also allow you to revert to older versions (more information can be found at http://www.motio.com/products/ci/overview.do).
There are also similar tools from BSP Software (www.bspsoftware.com) and Envisn (www.Envisn.com) that provide version controlling as well as other administration tasks such as scheduling, migration, and monitoring.