Delete old logs doesn't work

I activated the deletion of the logs, but it doesn’t work. The last scheduled deletion was this night, but all logs are still there. I tried to investigate some hints in the server logs, but I didn’t even find the start of the scheduled deletion. How does it work? Is a cronjob installed? How can I isolate my error? Who determines the time of the scheduled deletion?

Piwik 1.5 installed.
Automatic archive processing is set up.

delete_logs_enable = 1
delete_logs_schedule_lowest_interval = 1
delete_logs_older_than = 60
delete_max_rows_per_run = 1000

Without doing anything it seems to work now and I see the notice “Last deletion was on: …”. :slight_smile:

But the output in the is quite confusing. Sometimes it is:

Starting Scheduled tasks…
Piwik_CoreAdminHome.optimizeArchiveTable,Time elapsed: 0.325s
Piwik_PDFReports.dailySchedule,Time elapsed: 0.020s
Piwik_PrivacyManager.deleteLogTables,Time elapsed: 4.327s
Finished Scheduled tasks.

But sometimes it is:
Starting Scheduled tasks…
No data available
Finished Scheduled tasks.

Is that normal? Do the scheduled tasks work but not the output?

scheduled tasks are executed only once a day