Search notes:

Oracle database: Data file

The locations of a database's data files are recorded in the control file.
The data file stores the last checkpoint SCN.
Image copies of a data file might be stored in the fast recovery area.
In the data dictionary, data files are listed under dba_data_files.

Permanent and temporary data files

Oracle distinguishes between

Online and offline data files

A data file is either online or offline.
The data in an offline data file cannot be accessed until it is brought online.
Reasons to take a data file offline:
Oracle will automatically bring a data file offline if it cannot write to it anymore.

Alloction unit blocks

The data file is a physical file. When Oracle needs to allocate more space for a data file, that is, to grow the physical file, it does so by allocating that space in the logical units of data blocks.
The maximum number of data blocks that can be allocated for a data file is operating system dependent, typically, it is 222-1 blocks.

Size of data files

The size of a data file should be a multiple of the extent size of the tablespace the data file belongs to plus one block for the file header.

SQL statements

alter database move datafile …

See also

Oracle files, temp files
v$datafile and dba_data_files.
The input files for SQL*Loader are called data files. These must not be confused with the Oracle database data files!
Bypassing the buffer cache with direct path insert and read
The create database statement
data file header
The maximum number of data files that can be opened in a database is specified with the db_files init parameter. Regardless of this parameter's value, it cannot be more than 65533 data files.
data file checkpoint
dbms_space.isdatafiledroppable_name checks if a data file can be dropped.
The maximum number of data files is recorded in dba_high_water_mark_statistics.
$ORACLE_HOME/bin/dbv is the datafile verifier tool.
$ORACLE_HOME/bin/dbfsize determines a database file's type and size.
x$kccfn

Index