Encrypting datafiles online does not immediately release disk space from OS

Hi,

We are running the following command to encrypt our tablespace online(there are about 150 datafiles listed here). It works as expected as it goes through each datafile, copies it to the encrypted name, then deletes the old file from the OS. The problem is as after it deletes the file the space is never freed up from the OS until hours and hours later. This is causing the filesystems to fill up eventually. It took about 20 hours until the space started to be released from the filesystem. Is there anything we can do to ensure the space is actually