Hi Carlos,
In general, a single user won't affect much on your system. However, if you really want to scan at user level, try using ST03 to do more analysis.
Also, look what queries are running look at sm50 and dbacockpit. Use st02 to help in understanding the buffer state.
It becomes a concern when dialog process is going in private mode.
Refer https://help.sap.com/saphelp_nw04/helpdata/en/02/96279d538111d1891b0000e8322f96/content.htm
Regards