Summary
When trying to logon to WebCenter, the following error message appears: "Fatal error communicating with application server...RMI class loader disabled", indicating WebCenter is unable to connect to the database.
Symptoms
When trying to logon to WebCenter, the error as shown in the screenshot appears:

Solution
This error indicates that WebCenter is unable to connect to its "WebCenter4_0" database.
The cause can be specific WebCenter or WebCenter database problem or general SQL server problems.
You can find where WebCenter expects its database to be in the wc5-ds.xml
file located in C:\Esko\Artios\WebCenter\ApplicationServer\Jboss\server\default\deploy

In the screenshot above, the WebCenter4_0 database is expected at the SQL Server with hostname "HBDS1209" and more specifically in the instance "webcenter".
General problems with the SQL Server
- Verify if the SQL server (instance) is running.
- Verify if you can connect to the server instance via SQL (Express) Management Studio.
- Verify if the WebCenter4_0 is appearing.
- Check the properties of the database.
In case you encounter issues with the suggestions above, contact your local database administrator or read below.
WebCenter Problem
In many cases the cause is related to WebCenter being configured (during installation) to connect to its database in SQL Server instance where the WebCenter4_0 database is not actually located. To resolve such a situation you have two options:
Option 1: Modify the wc5-ds.xml
file (use Notepad or Notepad ++) to indicate the right location of the WebCenter4_0 database. Or
Option 2: Add the WebCenter4_0 database to the location indicated in the wc5-ds.xml
file. Keep reading!
WebCenter Database Problem
In some cases the problem could be caused by an incomplete database migration (restore). Mind that Option 2 specified in the solution part of the "WebCenter Problem" can also cause this.
After restoring the WebCenter4_0 database, the user "webcenter" of the database is not linked to the SQL instance "webcenter" login. The easiest way to create this link (and to create the login) is to use the Database Engine Query feature of SQL (Express) Management Studio as indicated below:

If you are not familiar with SQL, it is suggested to ask assistance.
When checking the properties of the "webcenter" user, the result should always be as indicated below:
