Multiplexing the Online Redo Log

Oracle recommends that you multiplex the online redo log. Multiplexing provides better protection for data if an instance or media failure occurs. You can multiplex the online redo log using Oracle Enterprise Manager Database Express (EM Express).

To multiplex your online redo log, you must add members to each online redo log group. It is not required that online redo log groups be symmetrical, but Oracle recommends that your groups all have the same number of members. A database must have a minimum of two online redo log groups.

Note:

When you multiplex the online redo log, the database must increase the amount of I/O that it performs. Depending on your configuration, this action may affect overall database performance.

To multiplex the online redo log:

  1. In EM Express, from the Storage menu, select Redo Log Groups.

    The Redo Log Groups page appears.

  2. Select a group and click Add Member.

    The Add Member page appears.

  3. In the File Directory field, enter the directory where you want the data file to be stored on disk.

    You can create this file in the same directory as the other member of the redo log file group, but it is recommended that you store members on separate disk drives. That way, if there is a drive failure, then you still have access to one member.

  4. In the File Name field, enter a file name for the new redo log member.

    For example, if your existing member file name is REDO01.log, then you might name this member REDO01a.log.

  5. Click OK.

    A confirmation message appears.

  6. Repeat Step 2 through Step 5 for every existing log group.