System names are selected during installation. The current system name is found by examining the clipboard value pxProcess.pxAdminSystem.pxSystemName on the Process page.
A system name can be changed after installation by clicking Designer Studio > System > Settings > System Name.
Your system can include more than one Data-Admin-System instance. However, only one is in current use, identified by the Identification/SystemName value in the prconfig.xml file or Dynamic System Settings.