Architecture Overview

Oracle is designed to be a very portable database—it is available on every platform of relevance, from Windows to UNIX to mainframes. However, the physical architecture of Oracle looks different on different operating systems. For example, on a UNIX operating system, you’ll see Oracle implemented as many different operating system processes, virtually a process per major function. On UNIX, this is the correct implementation, as it works on a multiprocess foundation. On Windows, however, this architecture would be inappropriate and would not work very well (it would be slow and nonscalable). On the Windows platform, Oracle is implemented as a single process with multiple threads. On IBM mainframe systems, running OS/390 and z/OS, the Oracle operating system-specific architecture exploits multiple OS/390 address spaces, all operating as a single Oracle instance. Up to 255 address spaces can be configured for a single database instance. Moreover, Oracle works together with OS/390 Workload Manager (WLM) to establish the execution priority of specific Oracle workloads relative to each other and relative to all other work in the OS/390 system. Even though the physical mechanisms used to implement Oracle from platform to platform vary, the architecture is sufficiently generalized that you can get a good understanding of how Oracle works on all platforms.