Upgrading to SQL 2014: Report Server version mismatch

Symptom
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If you have recently upgraded your SQL Server Reporting Services instance from SQL 2012 SP2 to SQL 2014, you may hit the following error message when trying to access your report server:

The version of the report server database is either in a format that is not valid, or it cannot be read. The found version is ‘163’. The expected version is ‘162’. (rsInvalidReportServerDatabase).

Cause
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As part of a hotfix for SQL 2012 SP2 CU5, a change was made which resulted in a new ReportServer database version. Since this fix was made after the SQL2014 release, if your SQL2012 SP2 server is on CU5 or later, then it will have a higher database version than what SQL2014 RTM expects.

Solution
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We are porting the fix in the next cumulative update for SQL 2014, CU7. In order to fix the version mismatch, you should install CU7 or later onto your SQL2014 instance, which will allow the Reporting Services instance to correctly recognize the new database version.

Notes
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If you have not yet upgraded, you can determine whether you will run into this issue by executing the following query against your ReportServer database:

SELECT MAX([DbVersion]) FROM [dbo].[DBUpgradeHistory]