As far as I know, the rec/client parameter must be active for table logging in SAP to be activated. This is a system-wide setting and becomes active after the profile parameters (RZ10) are changed and the SAP application restarted.

Please refer to SAPNET NOTE 139418 for more general information on logging user actions.

For custom-developed tables, you will need to turn on table logging at the table level:

Transaction SE11.
Enter Table Name in the Data Dictionary.
Click on Change.
Press the Technical Settings button.
Check the "Log data changes" checkbox at the bottom of the screen.

Table DD09L shows which tables are marked for table logging.

At a minimum, you should be logging changes to tables T000, T001 and DEVACCESS.

Use transaction SCU3 to check which tables were changed and by whom. This should be reviewed periodically by management for potential unauthorized changes. All changes should be linked to an approval/change ticket/change request/other relevant approval document.