ORACLE INSTANCE

Oracle instance is a collection of memory structures and processed that are used to manage oracle database. Each oracle database is to be accessed by one or more Oracle instances. If two or more instances are accessing the same database, it is called as parallel server architecture. In order to start using an oracle database, we must first start Oracle instance. Oracle instance will them open the database and make it available to users. It is beyond the scope of this book to discuss what Oracle instance actually contains. Please read “Oracle Concepts” manual for complete information about oracle instance. In nutshell every oracle installation contains at least one Oracle Instance and one oracle database

What Is Personal Oracle? 

Personal Oracle is one of the flavors of Oracle. This is not a product that is used by production system (systems where real data is stored). This is more like a learning tool. It runs on desktop PCs. In personal oracle, oracle instance, oracle database and client application all run on the same machine (see figure 3). Whereas in Oracle database server, only oracle instance and database reside on the server and client applications run on clients.

It is also possible to develop an applications using Personal Oracle on you desktop/laptop and deploy them in a client/server environment.