A publisher policy file can be distributed by the publisher of the assembly along with the update fix to a shared assembly.
The publisher policy file directs all references from an older assembly version to the newly installed version. Unlike the application configuration files, publisher policy files must be deployed in the global assembly cache (GAC) to become functional.
The settings in the publisher policy file override the version information that comes from the application or application configuration file. However, specific applications can be set up to ignore the publisher policy file by enforcing “safe mode.” Refer to the MSDN Library at http://msdn2.microsoft.com/en-us/default.aspx for information on setting applications to use safe mode.
Updates to Adaptive Server ADO.NET Data Provider usually include a publisher policy file that redirects applications to the latest installed version of the Data Provider assembly. It deploys the new provider assembly and the publisher policy file in the GAC.