Unable to connect SQL Server 2008 after SP3 is installed (Microsoft SQL Server, Error: 18401)

I recently installed SP3 for SQL Server 2008. Before installing the SP as usual I stopped all SQL services. My understanding is if SQL services are running then it will show up in blocked files list while installing service pack.

The install ran fine and after installation it asked to reboot the server which I did.

However after server reboot I was unable to connect to SQL server with following error.

TITLE: Connect to Server

Cannot connect to MYSERVER.

ADDITIONAL INFORMATION:

Login failed for user 'domain\login'. Reason: Server is in script upgrade mode. Only administrator can connect at this time. (Microsoft SQL Server, Error: 18401)

For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&EvtSrc=MSSQLServer&EvtID=18401&LinkId=20476

BUTTONS:

OK

I checked the SQL services and they were running fine. So why this error?

After installing Service pack SQL setup run some upgrade scripts namely “sqlagent100_msdb_upgrade.sql”

Following message was logged in SQL error log

2012-04-09 11:31:26.820 spid13s      ----------------------------------------------------------------

2012-04-09 11:31:26.820 spid13s      msdb_upgrade_discovery starting

2012-04-09 11:31:26.960 spid13s      MSDB format is: SQL Server 2008

2012-04-09 11:31:27.100 spid13s      User 'sa' is changing database script level entry 4 to a value of 2.

2012-04-09 11:31:27.120 spid13s      User 'sa' is changing database script level entry 5 to a value of 2.

2012-04-09 11:31:27.130 spid13s      User 'sa' is changing database script level entry 6 to a value of 2.

2012-04-09 11:31:27.130 spid13s      User 'sa' is changing database script level entry 6 to a value of 0.

2012-04-09 11:31:27.130 spid13s      Running SQL Server 2005 SP2 to SQL Server 2008 upgrade script

2012-04-09 11:31:27.130 spid13s      ----------------------------------------------------------------

What is the resolution?

Resolution is to just wait for few minutes till this upgrade script completes. I have seen some other blogs mentioning to turn of implicit transactions etc but in my case resolution was to WAIT and try connecting after few minutes