If you want to stop users using a tablespace, you can bring it offline using the ALTER TABLESPACE ... OFFLINE statement as shown in the following script:

SQL> connect HR/globalguideline

Connected.

SQL> CREATE TABLESPACE my_space

2 DATAFILE '/temp/my_space.dbf' SIZE 10M;

Tablespace created.

SQL> ALTER TABLESPACE my_space OFFLINE NORMAL;

Tablespace altered.

After bringing a tablespace offline, you can backup or rename the data file safely.