In SharePoint 2010 when you upgrade to a new Cumulative Update or Service Pack this involves two main steps – first is loading the binaries, and the second is running the SharePoint Server 2010 configuration wizard (psconfig or psconfigui). SharePoint supports delaying the running of the configuration wizard or even detaching content databases while running the wizard, so that these perhaps slow parts of the process can be managed in a more timely fashion. If you look at a SharePoint farm that is in this condition you will see in Central Administration, Upgrade and Migration, Review database status, that it says against many of the databases (Content, Config, and Admin Content) – Database is in compatibility range and upgrade is recommended. However, if you have Project Server installed then you will see against all of its databases (certainly for SP1/June CU) – Database is too old and upgrade is required. Some other databases such as BDC or PPS ones may just say No action is required if there were no updates for schema in the particular release. For some CUs you might see this for Project and the SharePoint content databases too.
If you ignore this message and try and go to PWA then you will get an error message: Error, Project Web App cannot connect to Project Server. For more information, contact your system administrator. – along with a GUID for tracking the full error in the logs.
Looking in the logs you will find the following exception and unexpected level records – which are pretty self explanatory.
08/23/2011 09:46:41.85 w3wp.exe (0x1724) 0x0FC0 Project Server General g7ls Exception System.ServiceModel.FaultException`1[Microsoft.Office.Project.Server.Interfaces.DefaultServerFault]: The databases are out of the range of compatibility, upgrade your databases. (Fault Detail is equal to Microsoft.Office.Project.Server.Interfaces.DefaultServerFault). fe5f9380-1f54-4021-a6a2-5fe7d3e321e8
08/23/2011 09:46:41.85 w3wp.exe (0x1724) 0x0FC0 SharePoint Foundation Runtime tkau Unexpected System.ServiceModel.FaultException`1[[Microsoft.Office.Project.Server.Interfaces.DefaultServerFault, Microsoft.Office.Project.Server.Communications, Version=220.127.116.11, Culture=neutral, PublicKeyToken=71e9bce111e9429c]]: The databases are out of the range of compatibility, upgrade your databases. Server stack trace: at System.ServiceModel.Channels.ServiceChannel.HandleReply(ProxyOperationRuntime operation, ProxyRpc& rpc) …
So to answer the question in the title – No, you cannot delay the running of the configuration wizard if you are using Project Server if there are database updates required in the particular patch you have loaded. Not every CU will require database changes – but rememeber these are cumulative, so the need for the database update will also depend at what level your server is when applying the patch.
*** Update based on feedback from one of my favorite customers - if you really cannot run the config wizard for a while then it will only be PWA that won't work. The Project sites will still work (apart perhaps from issues/risks/deliverables lists) and of course all the other SharePoint features and Central Administration will be just fine. ***