Mukund Yadav's Blog on OEM and APPS R12

Here are the steps to know Database growth pattern for last one month/year using OEM

1) Login to OEM and Click on the Reports Tab
2) Navigate to Reports-->Storage-->Oracle Database Space Usage path and Click on Oracle Database Space Usage link.
3) Select the Target database and here we are getting Oracle Database space usage for last one Month.
4) Also we can get one year Database growth by setting Set Time Period Button.
5) Also we can find Oracle Database Tablespace Monthly Space Usage by Navigating Reports-->Storage-->Oracle Database Space Usage path and click on Oracle Database Tablespace Monthly Space Usage link.

I hope this helps DBA's to plan for future disk space requirements.