Architecture

Oracle9i architecture consists of either single instance or multi-instance databases. Up until now, this book has been discussing multi-instance architecture. Let us digress and put this in context with the total Oracle9i picture. Figure 4.7 shows the Oracle9i single instance architecture.

Figure 4.7: Oracle9i Structures

As you can see, the overall structure of an Oracle9i single-instance database is fairly complex. A complete Oracle9i instance consists of disk files, shared memory structures, and background processes. The shared memory area is further subdivided into numerous caches and pools that are used to transfer data, programs, and instructions from processes to and from the disks and users. Let's start our examination of the Oracle9i architecture by looking at the background processes in a single-instance database.