Adding Redo Log Group Members

You can use the alter database add logfile member command to add extra member(s) to a redo log group. You might do this:

 

(1)  To add an extra member on a different disk and remove a single point of failure.

(2)  In conjunction with the alter database drop logfile member, to move a redo log group from one disk to another.

 

You can tell Oracle where to add the new member by giving a group number:

 

SQL> select group#, member from v$logfile;

 

    GROUP# MEMBER

---------- ----------------------------------------

         2 /disk1/redo/log2a.rdo

         1 /disk1/redo/log1a.rdo

 

SQL> alter database add logfile member

  2  '/disk2/redo/log1b.rdo'

  3  to group 1;

 

Database altered.

 

SQL> select group#, member from v$logfile;

 

    GROUP# MEMBER

---------- ----------------------------------------

         2 /disk1/redo/log2a.rdo

         1 /disk1/redo/log1a.rdo

         1 /disk2/redo/log1b.rdo

 

SQL>

 

Or by providing the name(s) of the members already in the group:

 

SQL> select group#, member from v$logfile;

 

    GROUP# MEMBER

---------- ----------------------------------------

         2 /disk1/redo/log2a.rdo

         1 /disk1/redo/log1a.rdo

         1 /disk2/redo/log1b.rdo

 

SQL> alter database add logfile member

  2  '/disk2/redo/log2b.rdo' to

  3  '/disk1/redo/log2a.rdo';

 

Database altered.

 

SQL> select group#, member from v$logfile

  2  order by 1, 2;

 

    GROUP# MEMBER

---------- ----------------------------------------

         1 /disk1/redo/log1a.rdo

         1 /disk2/redo/log1b.rdo

         2 /disk1/redo/log2a.rdo

         2 /disk2/redo/log2b.rdo

 

SQL>