When the session recording file purging is actually done based on the purge policy?
Configuration > Logs > Session Recording > Purge Policy
The purge script is executed at 0:00 in UTC every day based on the cron setting in PAM server.
You would see below log in Session logs around at 0:00 in UTC.
yyyy/mm/dd 0:03 sessionPurging PAM-CMN-1984: Session recording purging successfully completed. <n> recordings was/were removed.
For example, in Sydney/Australia GMT+11 (during daylight saving) will show the session recording purge run at 11:00AM local time.