Explain the types of data files
used by the oracle RDBMS.
Oracle file types - Jan 28, 2009 at 18:00 PM by Amit Satpute
Explain the types of data files used by the oracle RDBMS.
Online redo log files
A control file contains information such as location of redo log
files, backup data and redo log information.
The control file is updated to reflect the structure changes every time a
datafile or a redo log file is added or dropped from the database. These
records are necessary to identify datafiles and redo log files during startup
and recovery.
Archive log files
Archived log files are redo logs that Oracle fills with redo entries
that are rendered inactive and copied to one or more log archives.
Running the database in ARCHIVELOG mode has the following benefits:
-
Complete recovery of database from instance and media failure.
-
Performing online backups.
-
Transmitting and applying archived redo logs to the standby database.
-
Multiplexed archive logs to avoid single point of failure on the archive logs.
-
More recovery options (tablespace-point-in-time recovery)
Initialization files
Initialization parameter file is a text file in ASCII which contains
information needed to initialize a database and instance.
Control files
Control Files contain:
-
The physical structure of a database
-
Database name,
-
Names and locations of associated databases and online redo log files,
Timestamp of database creation,
-
Current log sequence number
-
Checkpoint information.
SGA definition files
System Global Area
The System Global Area (SGA) is a shared memory region that contains data and
control information for one Oracle instance. When an instance starts, the SGA
is allocated by Oracle and is deallocated when the instance shuts down. Every
instance has an own SGA.
Online Users share the data in the SGA.
The information stored in the SGA is divided into memory structures like:
-
The database buffers
-
Redo log buffer
-
The shared pool.
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