Symptoms:

When you try to remove a not used SQL Server from Sharepoint in the Central admin:

An object in the SharePoint administrative framework, "SPDatabaseServiceInstance Name= could not be deleted because other objects depend on it. Update all of these dependants to point to null or different objects and retry this operation. The dependant objects are as follows: SPWebService Name=WSS_Administration

Workaround:

You have switched to a new SQL server but SharePoint kept a reference. You can use an existing correct Web application to update Central admin with the good one:

$centralAdmin=Get-SPWebApplication -IncludeCentralAdministration | ? {$_.DisplayName -match ‘SharePoint Central Administration’}
$goodExample=Get-SPWebApplication -identity ‘http://mygoodwebapp’
$centralAdmin.Parent.DefaultDatabaseInstance=$goodExample.Parent.DefaultDatabaseInstance
$centralAdmin.Parent.Update()
$centralAdmin.Update()

Use SQL Alias for the next time

You may already have seen this SharePoint warning:

Object Cache: The super user account utilized by the cache is not configured. This can increase the number of cache misses, which causes the page requests to consume unneccesary system resources.
 To configure the account use the following command 'stsadm -o setproperty -propertyname portalsuperuseraccount -propertyvalue account -url webappurl'. The account should be any account that has Full Control access to the SharePoint databases but is not an application pool account.

I use the following script (all my web Applications are in claim):
foreach ($a in (Get-SPWebApplication))
{
   $a;
   $a.Properties["portalsuperuseraccount"];
   $a.Properties["portalsuperreaderaccount"];
   $a.Properties["portalsuperuseraccount"] =“i:0#.w|mydomain\SharePointAdminAccount“;
   $a.Properties["portalsuperreaderaccount"] =“i:0#.w|mydomain\SharePointDedicatedReadAccount“;
   $a.Update();
}

But none of them had an incoorect value. To find out quickly, just need to switch on the detail of the event:

You will find the PID (Process ID) which generated the error:

You then just have to use  Process Explorer for example to identify the web site:

In this case it was the Central admin, who shouldn’t be in claim anyway

While trying to add an item to a SharePoint List, i had the following error message:

Unable to index into an object of type Microsoft.SharePoint.SPListItem.
 + $newItem[ <<<< "column_name"] = $SPFieldUserValue
 + CategoryInfo : InvalidOperation: (column_name:String) [], RuntimeException
 + FullyQualifiedErrorId : CannotIndex

Column name are case sensitive, and i had forgotten a caps !