I am having issues when working with Custom fields, that the CRM gets frozen, and have to restart everything. Today I noticed that the MySQL table log_civicrm_custom_field has nearly 140K rows, while I have less than 400 custom fields only. There are hundreds of duplicated rows for each of the custom field, with the same id repeated but different log_date and log_conn_id. Is it natural to have this many log records, can we disable this logging? Or is there a way to clear some of these rows, so that the CRM works faster.
It might well be natural to have that many log records as they reflect changes that have been made to the fields. So if a field gets a new label or a new option, that would be reflected in the log tables.
You can disable the overall logging (Administer>System Settings>Misc) if you do not need it. It is not required to make CiviCRM run.
You can also elect to keep logging switched on but empty the logging tables regularly? You have to do that in the database, there is no user interface to empty the logging tables.
It could well be however that you switch off logging and your problem persists because that is not the root of the problem? I have so far not experienced the size of the logging tables leading to this behaviour, even with millions of records in it.