from my recently post download SharePoint patch
I've got an failure update content database on my SharePoint server farm shown with below picture.

I searched for the solution and found some recommendation from the Microsoft websites

http://technet.microsoft.com/en-us/library/cc262967.aspx

http://technet.microsoft.com/en-us/library/ff382638.aspx#FarmRestart

http://technet.microsoft.com/en-us/library/ff608074.aspx

then I checked the PSConfig.exe log file and found some clue why my upgrade was failed.

[OWSTIMER] [SPContentDatabaseSequence] [ERROR] [11/10/2011 2:23:08 PM]: Found a missing feature Id = [a18927ed-93e2-4dcb-be6d-56c469beb929]

[OWSTIMER] [SPContentDatabaseSequence] [ERROR] [11/10/2011 2:23:08 PM]: The feature with Id a18927ed-93e2-4dcb-be6d-56c469beb929 is referenced in the database [MYContentDatabase], but is not installed on the current farm. The missing feature may cause upgrade to fail. Please install any solution which contains the feature and restart upgrade if necessary.

the log file said, there's a missing custom feature i had deployed on MyContentDatabase. So I retracted and remove my custom solution and run this command to upgrade the content database again

psconfig -cmd upgrade -force -inplace v2v -passphrase < passphrase > -wait

the command will upgrade my content database then I redeploy my solution into the content database again.