Starting from Plesk 11.5, you can configure logging in the [log] section of the panel.ini file.

To enable or disable logging of SQL queries performed on the Plesk database, use the log.show.sql_query parameter, for example:

log.show.sql_query=true

To enable or disable the support for multithreaded logging, use the log.show.thread parameter, for example:

log.show.thread=true

See more parameters in the panel.ini.sample file.