This operation can be performed only on a computer that is joined to a server farm by users who have permissions in SQL Server to read from the configuration database. To connect this server to the server farm, use the SharePoint Products Configuration Wizard, located on the Start menu in Microsoft SharePoint 2010 Products

SHAREPOINT ISSUE :


Server Error in '/' Application.

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This operation can be performed only on a computer that is joined to a server farm by users who have permissions in SQL Server to read from the configuration database. To connect this server to the server farm, use the SharePoint Products Configuration Wizard, located on the Start menu in Microsoft SharePoint 2010 Products.

CAUSE

This issue would occur if the user account  “UserAccountName” or “Administrator” doesn’t have enough permission in the SQL server contents databases of SharePoint site collections .

SOLUTION  1

1. Go to SQL Server Management Studio Server
2. Expand the Security option -- Expand the logins -- Right click on the admin  account --
    Go to properties
3. Click on Server Roles--Enable the Sysadmin permission.
4. Do a IISRESET in Sharepoint server

SOLUTION 2

1. Go to SQL Server Management Server
2. Expand the Security option -- Expand the logins -- Right click on the admin account --
Go to properties
3. Click on User mappings-- Select Contenet database of the site collection --Provide DBreader permission
4. Do a IISRESET in Sharepoint server

SOLUTION 3

 If this issue happens after changing the farm admin password, Please update the passwrod in the Sharepoint

SOLUTION 4

Try running the Sharepoint configuration withouyt disconnecting the farm and make sure wizard completes successfully. If Wizard fails , Check the Log and let me know

Hope this helps you !