What is the sysadmin user for in WebCenter Content 11g?

The primary administrative user ID in WebCenter Content 11g out-of-the-box is the weblogic user. This user and password is created when the WebLogic Domain is created.

So what is that sysadmin user in the User Admin Applet? And what is the sysadmin password?

Out-of-the-box WebCenter Content uses the Oracle WebLogic Server User Store to manage user names and associated passwords. Typically, user management is handled in the Oracle WebLogic Server Administration Console instead of the WebCenter Content User Admin applet. If you create a user only through WebCenter Content User Admin Applet Oracle WebLogic Server does not recognize that user. These kinds of users are called local users.

The sysadmin user can be used to run the stand-alone administration applets. Before you can do that you need to use the User Admin Applet to change the default, randomly encoded password that the sysadmin user is created with.

You might also create local users for integration activities like web service calls or using UXIdcCommand.