Basics of Oracle Database Architecture

Oracle Database architecture consists of two main components: the database and the instance. Here's a brief overview of each component and their subcomponents: *1. Database:* The database is the physical storage component of the Oracle architecture. It contains datafiles, redo log files, and control files. - Datafiles store user data and database objects like tables, indexes, and clusters. - Redo log files record changes made to the database, allowing for recovery in case of failures. - Control files store the database's physical structure, such as tablespaces, datafiles, and redo log files. *2. Instance:* The instance is the memory and processes component of the Oracle architecture. It consists of the System Global Area (SGA) and background processes. - System Global Area (SGA): This is a shared memory area that stores data and control information for the database instance. The SGA includes the database buffer cache, shared pool, redo log buffer, and other memory structures. - Background processes: These are processes that run in the background, managing various tasks, such as managing database memory structures (DBWn), writing redo log entries (LGWR), monitoring and archiving redo log files (ARCH), and handling other tasks (CKPT, PMON, SMON, RECO). When a user connects to an Oracle database, the instance retrieves data from datafiles and caches it in the SGA. The user's actions generate redo log entries, which are used for recovery if needed. Background processes manage resources and ensure the database functions smoothly.