What does frequency and start time means in Magento admin log cleaning section?

Question

I want to know what does frequency and start time means in Magento admin log cleaning section?

I want to clean the logs every month. If I am setting start time 03:00:00, Frequency : monthly and the save log days to 29. Will it be working correctly?

Answer 1

Those 2 fields represent the cron settings.
From Start time you tell Magento at what hour the cron should run.
From Frequency you tell it how often the cron should run.

So basically setting the time 03:00:00 and frequency monthly will translate into the cron expression:

0 3 1 0 0

This means the cron will run each 1st of the month at 3 am and it will delete log entries older than 29 days.

But if you make the settings like this, there will be moments when you will have logs older than 29 days.
For example, the cron runs once on the 1st and after that you remain with only 29 days logs.
But on the 15th you will have 29 + 15 = 44 days logs.
This is not a problem, just pointed it out in case you don't want it like that.

Answer 2

You can select the starting time for the execution of the cron job, the frequency of the cleaning (daily, weekly, monthly), the error email recipient, etc. It's also recommended to decrease the value in the field for Save Log, Days. By default it's 180. If you enable log cleaning it's pointless to leave the default value because even if the cron job is executed daily or even monthly, the logs will still be saved for 180 days. So depending on your needs and preferences and on the frequency of cron job execution, decrease the value for Save Log, Days (e.g. 30 days, 7 days). After that click on the Save Config button in the upper right corner.

This LINK can be a good help.