How to debug and resolve CanUpgrade [SPConfigurationDatabase] failed issue

We have run into the following error several times and it’s a good time to record the solution.

In one of DEV SharePoint development box today, when we deploy solution and the solution was stay in deploying status. We also received timer job error and we are not able to deploy any solution. The log shows the following error.

04/18/2012 12:50:05.63 OWSTIMER.EXE (0x0494)                              0x27BC SharePoint Foundation                 Upgrade                                       fbv7       Unexpected       [OWSTIMER] [SPUpgradeSession] [ERROR] 

[4/18/2012 12:50:05 PM]: CanUpgrade [SPConfigurationDatabase] failed.          

04/18/2012 12:50:05.63 OWSTIMER.EXE (0x0494)                              0x27BC SharePoint Foundation                 Upgrade                                       fbv7       Unexpected       [OWSTIMER] [SPUpgradeSession] [ERROR] 

[4/18/2012 12:50:05 PM]: Inner Exception: The type initializer for 'System.Data.SqlClient.SqlConnectionFactory' threw an exception.    

04/18/2012 12:50:05.63 OWSTIMER.EXE (0x0494)                              0x27BC SharePoint Foundation                 Upgrade                                       fbv7       Unexpected       [OWSTIMER] [SPUpgradeSession] [ERROR] 

[4/18/2012 12:50:05 PM]:    at System.Data.SqlClient.SqlConnection..cctor()    

04/18/2012 12:50:05.63 OWSTIMER.EXE (0x0494)                              0x27BC SharePoint Foundation                 Upgrade                                       fbv7       Unexpected       [OWSTIMER] [SPUpgradeSession] [ERROR] 

[4/18/2012 12:50:05 PM]: Exception: The type initializer for 'System.Data.SqlClient.SqlConnection' threw an exception.              

… <Some error skipped here>

04/18/2012 12:50:05.63 OWSTIMER.EXE (0x0494)                              0x27BC SharePoint Foundation                 Timer                                         7v43       Medium               An error occured while initializing the timer.       

04/18/2012 12:50:05.63 OWSTIMER.EXE (0x0494)                              0x27BC SharePoint Foundation                 Timer                                         5utx       Unexpected       The timer service could not initialize its configuration, please check the configuration database.  Will retry later.

The error seems to indicate the upgrade and is very misleading. After debugging on the issue again, we realized this was the same issue we had before. The real error is in the application event log the DB is FULL. Here are two errors from SharePoint application event logs.

Now, it’s very clear that database is exceeding the limit. You could go to the location (our case is E:\SQL\Data) to review which DB is causing this issue. It’s as always the user profile sync application as in the following screen shot.

The solution is to shrink the DB and you will resolve the issue.