The database subsystem is used to communicate with external database servers and execute SQL queries from Unified CCX applications. The database subsystem is available only if the system has a license installed for either the Unified IP IVR or Unified CCX Premium product packages. If the database subsystem is not configured, it will show as out of service on the Control Center page of AppAdmin. This means that the database subsystem is not operational and cannot process any requests from the applications. To configure the database subsystem, you need to add database resources and specify the connection parameters for each database server that you want to access from your applications. You also need to enable the database subsystem from the Control Center page after adding the database resources. References: Cisco Unified Contact Center Express Administration Guide, Release 11.5 (1) - Database Subsystem Configuration