1.Add log file
SQL> alter database add logfile thread 1 group 7 ('+Q4DBFILE/ORADB/ONLINELOG/online7.dbf','+Q4DBFRA/ORADB/ONLINELOG/ronline7.dbf') size 500m reuse;
SQL> alter database add logfile thread 1 group 8 ('+Q4DBFILE/ORADB/ONLINELOG/online8.dbf','+Q4DBFRA/ORADB/ONLINELOG/ronline8.dbf') size 500m reuse;
SQL> alter database add logfile thread 2 group 9 ('+Q4DBFILE/ORADB/ONLINELOG/online9.dbf','+Q4DBFRA/ORADB/ONLINELOG/ronline9.dbf') size 500m reuse;
SQL> alter database add logfile thread 2 group 10 ('+Q4DBFILE/ORADB/ONLINELOG/online10.dbf', '+Q4DBFRA/ORADB/ONLINELOG/ronline10.dbf') size 500m reuse;
SQL> alter database add logfile thread 3 group 11 ('+Q4DBFILE/ORADB/ONLINELOG/online11.dbf', '+Q4DBFRA/ORADB/ONLINELOG/ronline11.dbf') size 500m reuse;
SQL>  alter database add logfile thread 3 group 12 ('+Q4DBFILE/ORADB/ONLINELOG/online12.dbf','+Q4DBFRA/ORADB/ONLINELOG/ronline12.dbf') size 500m reuse;

2.Switch log file
 alter system switch logfile;
check v$log to make sure old redo log is in inactive state.

3.Drop old log file
alter database drop logfile group 1;
alter database drop logfile group 2;
alter database drop logfile group 3;
alter database drop logfile group 4;
alter database drop logfile group 5;
alter database drop logfile group 6;
alter database drop logfile group 7;
alter database drop logfile group 8;