Database Reference
In-Depth Information
Chapter 2
Files in Support of Backup
and Recovery Operations
An Oracle database consists of three types of mandatory files: control files, online redo logs, and data files. This
chapter looks at the basics of managing these critical files. This chapter also discusses how to implement archiving
(which generates archive redo log files) and enabling a fast recovery area (FRA). Understanding how to enable
archiving and how to manage archive redo logs is a crucial part of database administration and backup and recovery.
It's also important to understand basic FRA concepts as RMAN (unless otherwise directed) will by default write
backup files to the FRA.
When working with RMAN, it's essential to understand the files that comprise the database. Being familiar with
the physical characteristics of your database lay the foundation for understanding how RMAN performs backup and
recovery operations. This knowledge will enable you to better understand the underlying mechanics and also provide
the base information required for troubleshooting when problems arise. First up is managing control files.
Managing Control Files
A control file is a small binary file that stores information such as the database name, names and locations of data
files, names and locations of online redo log files, current online redo log sequence number, checkpoint information,
and names and locations of RMAN backup files (if using). You can query much of the information stored in the control
file from data dictionary views. This example displays the types of information stored in the control file by querying
V$CONTROLFILE_RECORD_SECTION
:
SQL> select distinct type from v$controlfile_record_section;
TYPE
----------------------------
FILENAME
TABLESPACE
RMAN CONFIGURATION
BACKUP CORRUPTION
PROXY COPY
FLASHBACK LOG
...
