This is the article describing how to reduce Filespace when it is out of quota space.
There are a few ways to check available and used disk quota. Detailed information can be found in here.
Reducing disk quota after grace period passed
There is a 7 day grace period given to access your files safely and get the account under disk quota. Moving files is restricted after this period passed. If your filespace is grossly over quota, you will not be able to move files at all. The grace period will not apply. You must delete files until your account is below quota.
First thing you can do is empty the Recycle Bin and see if it brings the account under the quota, if it is delete files as outlined in above instructions.
If not, there are couple options to chose from:
1) use Linux machines to empty the trashcan in the Gui, or open up Terminal, and remove files using "rm file_name" command.
2) if using windows file explorer, highlight the files you wish to delete, and press Shift+Delete which will lead to "permanent" deletion of files.
If you still have problems with deleting files and going under the quota, contact CAE Help Desk.