If we want to resize the existing data file. We must use alter database datafile resize command.
Steps to resize using alter database datafile resize.
![alter database datafile resize alter database datafile resize](https://4.bp.blogspot.com/-bZrnImFJXTM/W1K6cGLYZHI/AAAAAAAAAUA/SwAMMe3B148mBXsfaItzgNUpHubyLRAIQCLcBGAs/w400-h243/alter_database_datafile_resize.png)
Before doing resize the data file in oracle database, we will have to check the existing data file size.
SQL>select file_name,bytes/1024/1024 SIZE_IN_MB from
dba_data_files where tablespace_name=’XXCUSTOM’;
Resize the oracle database data file using below command.
SQL>alter database datafile ‘/path/filename.dbf’ resize 6g;
To enable auto-extend on datafile, click here.
For additional information on Administering Database Size. Please check.👉alter tablespace add datafile.