No space is freed after Linux deletes files

In Linux or Unix systems, deleting files via RM or File Manager will be unlinked from the file system's folder structure (unlink). However, assuming that the file is

Open (a process is in use), the process will still be able to read the file and disk space is always occupied. And I deleted the Oracle's alarm log file.
The file should be in use when it is deleted.

First get a list of files that have been deleted but are still occupied by the application, as seen below: lsof |grep deleted

No space is freed after Linux deletes files