===== Redo Logs =====

==== Resizing Online ====

=== Add New Log Groups ===

If we are using OMF then all that is needed is the below 3 commands.
<code>ALTER DATABASE ADD LOGFILE GROUP 4 SIZE 500M;
ALTER DATABASE ADD LOGFILE GROUP 5 SIZE 500M;
ALTER DATABASE ADD LOGFILE GROUP 6 SIZE 500M;</code>

Without OMF then the following commands will be needed.
<code>ALTER DATABASE ADD LOGFILE GROUP 4 (
  2  '/u02/app/oradata/redo04a.log',  
  3  '/u03/app/oradata/redo04b.log') SIZE 500M;
ALTER DATABASE ADD LOGFILE GROUP 5 (
  2  '/u02/app/oradata/redo05a.log',  
  3  '/u03/app/oradata/redo05b.log') SIZE 500M;
ALTER DATABASE ADD LOGFILE GROUP 6 (
  2  '/u02/app/oradata/redo06a.log',  
  3  '/u03/app/oradata/redo06b.log') SIZE 500M;</code>
  
To add a log file to an existing redo log group ...
<code>ALTER DATABASE ADD LOGFILE MEMBER TO GROUP 1;</code>
Note that the status of the logfile will be invalid before it is used.

=== Check Status of Current Logs ===

<code>SELECT GROUP#, STATUS FROM V$LOG;</code>

=== Drop Old Logs ===

You cannot drop log files if their status is ACTIVE or CURRENT. \\

If the log file you want to drop is CURRENT then
<code>ALTER SYSTEM SWITCH LOGFILE;</code>

If the log file you want to drop is ACTIVE then
<code>ALTER SYSTEM CHECKPOINT GLOBAL;</code>

<code>ALTER DATABASE DROP LOGFILE GROUP 1;
ALTER DATABASE DROP LOGFILE GROUP 2;
ALTER DATABASE DROP LOGFILE GROUP 3;</code>

To drop individual log files from within a group ...
<code>ALTER DATABASE DROP LOGFILE MEMBER '<Full Filename>';</code>

=== View Current Log Files ===

<code>set linesize 120
col MEMBER format a60
SELECT A.GROUP#, A.MEMBER, B.BYTES
FROM V$LOGFILE A, V$LOG B WHERE A.GROUP# = B.GROUP#;</code>