Oracle Architecture

These are the basic descriptions of the oracle internals, don’t worry if you don’t grasp or

understood this immediately, most DBA’s take a few years to understand this. And in the real world, your clients or managers usually don’t ask you what’s the meaning of a oracle term. So don’t get discouraged! Would suggest to browse thru this and proceed to Further Tasks (Installing and creating the oracle database), where the fun stuff begins.

Main parts of the Oracle Architecture

1. Memory

- this is what inhabit the RAM on the computer, these structures only exist when the software is running

2. Processes

- exists when the instance is running

3. Files and Structures

- files associated with the database exist all the time, as long as the database is created Memory

                1. SGA(System Global Area)

                - this contains SQL statements and data

                2. Database Buffer Cache

                - contains data that comes from the files on disk, and because accessing data from       disk is slower that accessing from memory, the DB buffer cache main purpose is to           cache the data in memory

                3. Redo Log Buffer

                - stores every SQL statement that changes data

                4. Large Pool

                - this is used by Oracle Recovery Manager(this is the backup/restore tool of oracle)

                - when large pool is not configured it will get memory from the shared pool, which     could result in poor SQL execution Database Physical Structures

Files

1. Redo Log Files

- stores all the information needed to recover lost data

- has the extension .LOG(best practice)

2. Archive Log Files

- stores redo log copies to disk, used to restore a database from almost any type of failure

- has the extension .ARC(best practice)

3. Server and Initialization Files

- this is where the database parameter is configured, like memory size, db/instance name, archiving parameters, processes and many more

- has the extension .ORA(best practice)