oer+MySQL users have 2 choices. If you are running 1.0-25 or older you will have to manually create database tables for each channel you want oer+MySQL to log. Use the example scripts provided in the oer+MySQL/scripts directory, oer+MySQL will tell you the table name that should be created when you set channel flag "L" and/or channel flag "S". Beginning with oer+MySQL 1.0-26 you can set global flag "n" (set by default) to use 2 central tables for last and seen logging (those 2 tables are automatically created by "make install").

If you want you could use the old way of logging even with oer+MySQL 1.0-26 or newer. If you do, just remove the global flag "n" if it is set and create the database tables as explained above. A reason for prefering the old method over the new one is that it is more performant. If you don't plan to add new channels and your channels have a lot of channel activity (say more than 1000 lines per day) you may want to prefer the old method over the new one.