Online Redolog Files Management

To check the current Online Redo Log file information:

set linesize 200 pagesize 30
select group#,thread#,sequence#,bytes/1024/1024/1024 size_gb,members,archived,status

from v$log
order by group#;

set linesize 200 pagesize 30
col member for a50

select group#,type,member from v$logfile order by group#;

col member for a50

select a.group#, thread#,sequence#, bytes/1024/1024/1024 size_gb, members, 

a.status, type, member

from v$log a,v$logfile b

where a.group# = b.group#

order by a.group#;

Adding redo log group to the database

alter database add logfile
group 4 '/u01/prod/redo04a.log'
size 50m;

Droping redo log group from database

col member for a50
select group#, member from v$logfile order by group#;

alter database drop logfile group 4;

Adding redo log member to an existing group

alter database
add logfile member '/u01/prod/redo04b.log'
to group 4;

Drop  redo log member from the database

column member format a50
select group#, member from v$logfile order by group#;

alter database drop logfile member '/u01/prod/redo04b.log';

select group#, member from v$logfile order by group#;

Resizing redo log groups (create new ones and delete old ones after few log switches)

select group#, status, bytes/1024/1024/1024 size_gb from v$log order by group#;

alter database add logfile group 4 '/u01/prod/redo04.log' size 100m;

alter database add logfile group 5 '/u01/prod/redo05.log' size 100m;

alter database add logfile group 6 '/u01/prod/redo06.log' size 100m;

alter system switch logfile;

/

/

/

select group#, members, status from v$log order by group#;

now drop the old ones

alter database drop logfile group 1;

alter database drop logfile group 2;

alter database drop logfile group 3;

select group#, members, status, bytes from v$log order by group#;

now all will be of 100m size

https://docs.oracle.com/cd/A57673_01/DOC/server/doc/SAD73/ch5.htm#:~:text=To%20drop%20specific%20inactive%20online,DROP%20LOGFILE%20MEMBER%20'log3c'%3B