|Oracle® Database Administrator's Guide
11g Release 2 (11.2)
Part Number E17120-05
This section describes the various ways to alter the size of a datafile, and contains the following topics:
You can create datafiles or alter existing datafiles so that they automatically increase in size when more space is needed in the database. The file size increases in specified increments up to a specified maximum.
Setting your datafiles to extend automatically provides these advantages:
Reduces the need for immediate intervention when a tablespace runs out of space
Ensures applications will not halt or be suspended because of failures to allocate extents
To determine whether a datafile is auto-extensible, query the
DBA_DATA_FILES view and examine the
You can specify automatic file extension by specifying an
AUTOEXTEND ON clause when you create datafiles using the following SQL statements:
You can enable or disable automatic file extension for existing datafiles, or manually resize a datafile, using the
DATABASE statement. For a bigfile tablespace, you are able to perform these operations using the
The following example enables automatic extension for a datafile added to the
ALTER TABLESPACE users ADD DATAFILE '/u02/oracle/rbdb1/users03.dbf' SIZE 10M AUTOEXTEND ON NEXT 512K MAXSIZE 250M;
The value of
NEXT is the minimum size of the increments added to the file when it extends. The value of
MAXSIZE is the maximum size to which the file can automatically extend.
The next example disables the automatic extension for the datafile.
ALTER DATABASE DATAFILE '/u02/oracle/rbdb1/users03.dbf' AUTOEXTEND OFF;
See Also:Oracle Database SQL Language Reference for more information about the SQL statements for creating or altering datafiles
You can manually increase or decrease the size of a datafile using the
ALTER DATABASE statement. This enables you to add more space to your database without adding more datafiles. This is beneficial if you are concerned about reaching the maximum number of datafiles allowed in your database.
For a bigfile tablespace you can use the
TABLESPACE statement to resize a datafile. You are not allowed to add a datafile to a bigfile tablespace.
Manually reducing the sizes of datafiles enables you to reclaim unused space in the database. This is useful for correcting errors in estimates of space requirements.
In the next example, assume that the datafile
/u02/oracle/rbdb1/stuff01.dbf has extended up to 250M. However, because its tablespace now stores smaller objects, the datafile can be reduced in size.
The following statement decreases the size of datafile
ALTER DATABASE DATAFILE '/u02/oracle/rbdb1/stuff01.dbf' RESIZE 100M;
Note:It is not always possible to decrease the size of a file to a specific value. It could be that the file contains data beyond the specified decreased size, in which case the database will return an error.