Issue/Symptom/Question

How do I monitor the Oracle database tablespace in order to know when to add data files?

Applies To

Oracle

Resolution/Fix/Answer

Run the following query

select * From DBA_TABLESPACE_USAGE_METRICS order by used_percent desc;

If the USED_PERCENT value is 90 or higher, add data files. Refer to this article for more information: Adding a Database file

Cause 

Tablespaces grow over time as data is added.