Oracle Tuning Recommendations › Database Configuration › Increase Space in Redo Logs

Increase Space in Redo Logs

The number and size of the Redo log files is an important performance consideration. Redo log files are created when the database is created.

To increase space in the Redo logs

1. Log in to Oracle using SQL*Plus as SYSDBA or SYSOPER and run the following script to create eight Redo logs that are 2 MB each:

   rem -- parm1 -- temp dir
   

   rem Generate creation script
   SELECT 'ALTER DATABASE ADD LOGFILE '''
       ||  SUBSTR ( MEMBER , 1 , INSTR ( MEMBER , '\' , -1 , 1 ) )
       || 'REDO_11.LOG'' SIZE 2M ;'
     from V$LOGFILE
    where ROWNUM = 1
      and not exists ( SELECT 1 from V$LOGFILE where MEMBER like '%REDO_11.LOG' )
    UNION
   

   SELECT 'ALTER DATABASE ADD LOGFILE '''
       ||  SUBSTR ( MEMBER , 1 , INSTR ( MEMBER , '\' , -1 , 1 ) )
       || 'REDO_12.LOG'' SIZE 2M ;'
     from V$LOGFILE
    where ROWNUM = 1
      and not exists ( SELECT 1 from V$LOGFILE where MEMBER like '%REDO_12.LOG' )
    UNION
   

   SELECT 'ALTER DATABASE ADD LOGFILE '''
       ||  SUBSTR ( MEMBER , 1 , INSTR ( MEMBER , '\' , -1 , 1 ) )
       || 'REDO_13.LOG'' SIZE 2M ;'
     from V$LOGFILE
    where ROWNUM = 1
      and not exists ( SELECT 1 from V$LOGFILE where MEMBER like '%REDO_13.LOG' )
    UNION
   

   SELECT 'ALTER DATABASE ADD LOGFILE '''
       ||  SUBSTR ( MEMBER , 1 , INSTR ( MEMBER , '\' , -1 , 1 ) )
       || 'REDO_14.LOG'' SIZE 2M ;'
     from V$LOGFILE
    where ROWNUM = 1
      and not exists ( SELECT 1 from V$LOGFILE where MEMBER like '%REDO_14.LOG' )
    UNION
   

   SELECT 'ALTER DATABASE ADD LOGFILE '''
       ||  SUBSTR ( MEMBER , 1 , INSTR ( MEMBER , '\' , -1 , 1 ) )
       || 'REDO_15.LOG'' SIZE 2M ;'
     from V$LOGFILE
    where ROWNUM = 1
      and not exists ( SELECT 1 from V$LOGFILE where MEMBER like '%REDO_15.LOG' )
    UNION
   

   SELECT 'ALTER DATABASE ADD LOGFILE '''
       ||  SUBSTR ( MEMBER , 1 , INSTR ( MEMBER , '\' , -1 , 1 ) )
       || 'REDO_16.LOG'' SIZE 2M ;'
     from V$LOGFILE
    where ROWNUM = 1
      and not exists ( SELECT 1 from V$LOGFILE where MEMBER like '%REDO_16.LOG' )
    UNION
   

   SELECT 'ALTER DATABASE ADD LOGFILE '''
       ||  SUBSTR ( MEMBER , 1 , INSTR ( MEMBER , '\' , -1 , 1 ) )
       || 'REDO_17.LOG'' SIZE 2M ;'
     from V$LOGFILE
    where ROWNUM = 1
      and not exists ( SELECT 1 from V$LOGFILE where MEMBER like '%REDO_17.LOG' )
    UNION
   

   SELECT 'ALTER DATABASE ADD LOGFILE '''
       ||  SUBSTR ( MEMBER , 1 , INSTR ( MEMBER , '\' , -1 , 1 ) )
       || 'REDO_18.LOG'' SIZE 2M ;'
     from V$LOGFILE
    where ROWNUM = 1
      and not exists ( SELECT 1 from V$LOGFILE where MEMBER like '%REDO_18.LOG' )
   .
    Spool &1.AddLog.ORA
   /
   Spool Off
   COMMIT ;
   

   SELECT 'ALTER SYSTEM SWITCH LOGFILE ;' from V$LOG where ROWNUM < 5
   .
    Spool &1.SwtchLog.ORA
   /
   Spool Off
   COMMIT ;
   

   rem Generate Deletion script
   SELECT 'ALTER DATABASE DROP LOGFILE GROUP ' || TO_CHAR ( GROUP# ) || ' ;' from V$LOG where BYTES < 2097152
   .
    Spool &1.DropLog.ORA
   /
   Spool Off
   COMMIT ;
   

   @&1.AddLog.ORA
   $Del &1.AddLog.ORA
   COMMIT ;
    
   @&1.SwtchLog.ORA
   $Del &1.SwtchLog.ORA
   COMMIT ;
    
   @&1.DropLog.ORA
   $Del &1.DropLog.ORA
   COMMIT ;
   

2. Run the following query to verify the new Redo log configuration:

   SQLWKS> select group#, status, bytes from v$log;
   

Note: Oracle does not let you drop an older Redo log file that is still ACTIVE. If you must drop an older Redo log file that is still ACTIVE, drop that log file manually.