Oracle Database Storage Architecture

• Control files: Hold data about physical database structure information like Database Name, Data File and Redo Log file Names and locations. These files critical to the database. It can also contain metadata related to backups.
• Data files : Holds the user or application data of the database, as well as metadata and the data dictionary.
• Redo Log Files : Hold all the changes made to the database and allow for instance recovery of the database to retrieve the original information.

The following additional files are important to run database succefully :

• Parameter File: Holds the parameters (dbname, memory_max_target, processes, … ),  which defines the way the database is expected to start up.
• Password File: Allows user using administrator roles (like sysdba, sysoper, sysasm …) to connect remotely to the instance and perform administrative taks.
• Backup files : Used for database recovery.
• Archived redo log file : These are archive of redo log file which are preserved to support database recovery in case database crashes.
• Alert log file : Is a chronological log of messages and errors. Usually used to find related database errors.
• Trace files : When an internal error is detected by process, the process dumps information about the error to its trace file. Some of the information written to a trace file is intended for the database administrator, whereas other information is for Oracle Support Services.