Alter logfiles

Sometimes you want to change a logfile that's still in use. In order to clear it and drop it, execute following commands:

alter system checkpoint;
alter database switch logfile;  
alter system archive log all;
alter database drop logfile group 1;

Then you can add it again with a new size

ALTER DATABASE ADD LOGFILE GROUP 1 ('/db/redo01a.log', '/db/redo01b.log') SIZE 512M reuse;