The files that constitute an Oracle database are organized into the
following:
•
Control
files: Contain data about the database itself (that is, physical database
structure information). These files are critical to the database. Without them,
you cannot open data files to access the data within the database.
•
Data
files: Contain the user or application data of the database, as well as
metadata and the data dictionary
•
Online
redo log files: Allow for instance recovery of the database. If the
database server crashes and does not lose any data files, then the instance can
recover the database with the information in these files.
The following additional files are important to the successful running of
the database:
•
Parameter
file: Is used to define how the instance is configured when it starts up
•
Password
file: Allows sysdba/sysoper/sysasm to connect remotely to the database and
perform administrative tasks
•
Backup
files: Are used for database recovery. You typically restore a backup file when
a media failure or user error has damaged or deleted the original file.
•
Archived
redo log files: Contain an ongoing history of the data changes
(redo) that are generated by the instance. Using these files and a backup of
the database, you can recover a lost data file. That is, archive logs enable
the recovery of restored data files.
•
Trace
files: Each server
and background process can write to an associated trace file. When an internal
error is detected by a 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.
•
Alert
log file: These are
special trace entries. The alert log of a database is a chronological log of
messages and errors. Each instance has one alert log file. Oracle recommends
that you review this periodically.
