How to remove datafile carefully?

find datafile path;
SQL> 
select file_name from dba_data_files;

before run rm;
$ cd /oradata
$ lsof *
$ rm -f alper_data_01.dbf

How to transfer database file in Windows?

To do that please follow the instructions;

Tablespace: ALPER_DATA
Database file: data_01.dbf
DB file path: C:\Databasefiles
New database file name: data_new_01.dbf
New DB file path: D:\Databasefiles

Type these commands and press enter;

Example of offline transfer (database runs as non-archivelog mode)

Tablespace goes offline;

• sqlplus / as sysdba 
• alter tablespace ALPER_DATA offline;
• exit
• move C:\Databasefiles\data_01.dbf D:\Databasefiles\data_new_01.dbf

Datafile location info updates in database;

• sqlplus / as sysdba
• alter tablespace ALPER_DATA rename datafile 'C:\Databasefiles\data_01.dbf' to 'D:\Databasefiles\data_new_01.dbf';
• alter tablespace ALPER_DATA online;
• exit

Example of online transfer (database runs as archivelog mode)

Datafile goes offline;

• sqlplus / as sysdba
• alter database datafile 'C:\tablespaces\alper_01.dbf' offline;
• exit
• move C:\Databasefiles\data_01.dbf D:\Databasefiles\data_new_01.dbf

Datafile location info updates in database;

• sqlplus / as sysdba
• alter tablespace ALPER_DATA rename datafile 'C:\Databasefiles\data_01.dbf' to 'D:\Databasefiles\data_new_01.dbf';
• recover datafile 'D:\Databasefiles\data_new_01.dbf'
• alter database datafile 'D:\Databasefiles\data_new_01.dbf' online;
• exit

Bye :)

How to define a tablespace in Windows?

Please execute the commands as "sys";

To define the tablespace:
SQL> CREATE TABLESPACE ALPER_DATA 
DATAFILE 'C:\tablespaces\data_01.dbf' SIZE 128M

To alter the tablespace:
SQL> ALTER TABLESPACE ALPER_DATA ADD DATAFILE 'C:\tablespaces\data_new_02.dbf' size 128m;

To drop the datafile from the tablespace:
SQL> ALTER TABLESPACE ALPER_DATA DROP DATAFILE 'C:\tablespaces\data_new_02.dbf';

To drop the tablespace:
SQL> DROP TABLESPACE ALPER_DATA 
INCLUDING CONTENTS AND DATAFILES;

To check tablespace's database files:
SQL> SELECT NAME, FILE#, STATUS FROM V$DATAFILE;

Used Oracle Version and OS: Oracle XE and Win7