Chapter 2. Understanding Oracle Database Architecture

In This Chapter

  • Structuring memory

  • Checking the physical structures

  • Applying the irreducible logic of the logical structures

Understanding the Oracle architecture is paramount to managing a database. If you have a sound knowledge of the way Oracle works, it can help all sorts of things:

  • Troubleshooting

  • Recovery

  • Tuning

  • Sizing

  • Scaling

As they say, that list can go on and on. That's why a solid knowledge of the inner workings of Oracle is so important.

In this chapter we break down each process, file, and logical structure. Despite the dozens of different modules in the database, you should come away with a good understanding of what they are, why they're there, and how they work together. This chapter is more conceptual than it is hands-on, but it gives you a solid base for moving forward as you begin working with Oracle.

Defining Databases and Instances


In Oracle speak, an instance is the combination of memory and processes that are part of a running installation. The database is the physical component or the files. You might hear people use the term database instance to refer to the entire running database. However, it's important to understand the distinction between the two.


Here are some rules to consider:

  • An instance can exist without a database. Yes, it's true. You can start an Oracle instance and not have it access any database files. Why would you do this?

    • This is how you create a database. There's no chicken-or-egg debate here. ...

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