logger module logs data to a flat file.

logger_db module logs data to a MYSQL database.

Try these modules using the /mat/demo/basic_logger module

To test the logger_db module you should have a MYSQL connection available with
the database already created. The table is automaticaly created if it does
not exist. If a table with the same name exist in the database but the structure
is not compatible then the logger_db will not log, but if a table with the same
name exist and the structure is compatible then logger_db module will append 
rows to this table.

Also there is a commented line in /mat/demo/basic_logger/matplc.conf that
needs to be uncommented to test the logger_db module. This is because this
sample uses only the logger module by default.