Cannot add specified assembly to the global assembly cache during upgrade
During an upgrade of DocRead it is possible you will receive this error : “Cannot add specified assembly to the global assembly cache“. This error occurs because one or more of the DocRead assemblies are in being used. This will either be because a timer job is running, or because a a IIS is locking the DocRead assembly.
Important – please NEVER remove the existing WSPs as this initiates a full install and will remove DocRead and the tasks from your Farm. Always use upgrade.
To minimise the probability of this error occurring – it’s advisable to perform the following on all WFE and App Servers in your farm :
1. Temporarily disable all of the DocRead timer jobs from within Central Admin. You will need to enter each one and click “Disable”.
2. Run IISRESET from a command prompt
3. Recycle the SharePoint Timer Job (Windows Services Timer Job on 2007)
(Please note, it is also essential that these 2 actions are performed after an upgrade as well. This ensure the latest code will be used.)
If you do receive the error. Then just try the above again and try installing again. If all fails, you may need reboot your servers
Once the upgrade is complete, please re-enable all of the timer jobs.