The system to which you are upgrading (that is, your system as you expect it to exist after you upgrade).
A target system is one where the tests are executed on another platform (called the host system), but they are directed to test another system.
A system accessed by a procedural gateway or transparent gateway. For example, a data source, operating system, real-time system, process control monitor, and so on. Target systems are categorized by access category.
The system that the data is to be migrated into (normally an RDBMS system)