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3 Replies Latest reply: May 10, 2013 1:54 AM by FreddieEssex RSS

Archived logs are 5MBish when the ORL is 10mb !

Max Newbie
Currently Being Moderated
version: 10.2.0.4/RHEL 5.4

In our DB the Online Redo Logs are sized 10mb
SQL> select group#, bytes/1024/1024 from v$log;

    GROUP# BYTES/1024/1024
---------- ---------------
         1              10
         2              10
         3              10
But the archived redo logs are of size around 5mb.As you can see from the file sizes below, manual log switch/archiving is not happening.

Below are the archived redo log file in the location configured for LOG_ARCHIVE_DEST_1
-rw-r----- 1 oracle dba 5267456 May  7 22:00 kemsuat_1_655792404_95866.arc
-rw-r----- 1 oracle dba 5241856 May  7 22:00 kemsuat_1_655792404_95867.arc
-rw-r----- 1 oracle dba 5241856 May  7 22:00 kemsuat_1_655792404_95868.arc
-rw-r----- 1 oracle dba 6000640 May  7 22:00 kemsuat_1_655792404_95869.arc
-rw-r----- 1 oracle dba 5241856 May  7 22:00 kemsuat_1_655792404_95870.arc
-rw-r----- 1 oracle dba 5241856 May  7 22:01 kemsuat_1_655792404_95871.arc
-rw-r----- 1 oracle dba 5241856 May  7 22:01 kemsuat_1_655792404_95872.arc
-rw-r----- 1 oracle dba 6201344 May  7 22:23 kemsuat_1_655792404_95873.arc
-rw-r----- 1 oracle dba 5241856 May  7 23:13 kemsuat_1_655792404_95875.arc
-rw-r----- 1 oracle dba 5241856 May  7 23:13 kemsuat_1_655792404_95874.arc
-rw-r----- 1 oracle dba 5241856 May  7 23:13 kemsuat_1_655792404_95876.arc
-rw-r----- 1 oracle dba 5241856 May  7 23:13 kemsuat_1_655792404_95877.arc
-rw-r----- 1 oracle dba 5241856 May  7 23:13 kemsuat_1_655792404_95878.arc
-rw-r----- 1 oracle dba 5241856 May  7 23:13 kemsuat_1_655792404_95879.arc
-rw-r----- 1 oracle dba 8305152 May  7 23:13 kemsuat_1_655792404_95880.arc
-rw-r----- 1 oracle dba 5241856 May  7 23:13 kemsuat_1_655792404_95881.arc
-rw-r----- 1 oracle dba 5294592 May  7 23:13 kemsuat_1_655792404_95882.arc
-rw-r----- 1 oracle dba 7031296 May  7 23:14 kemsuat_1_655792404_95883.arc
-rw-r----- 1 oracle dba 5241856 May  7 23:14 kemsuat_1_655792404_95884.arc
-rw-r----- 1 oracle dba 5236736 May  7 23:45 kemsuat_1_655792404_95885.arc
-rw-r----- 1 oracle dba 5259264 May  8 01:15 kemsuat_1_655792404_95886.arc
-rw-r----- 1 oracle dba 5241856 May  8 02:50 kemsuat_1_655792404_95887.arc
-rw-r----- 1 oracle dba 5238784 May  8 04:30 kemsuat_1_655792404_95888.arc
-rw-r----- 1 oracle dba 5298176 May  8 06:06 kemsuat_1_655792404_95889.arc
-rw-r----- 1 oracle dba 5241856 May  8 07:30 kemsuat_1_655792404_95890.arc
-rw-r----- 1 oracle dba 5240320 May  8 09:00 kemsuat_1_655792404_95891.arc
-rw-r----- 1 oracle dba 5241856 May  8 09:44 kemsuat_1_655792404_95892.arc
-rw-r----- 1 oracle dba 5238784 May  8 10:15 kemsuat_1_655792404_95893.arc
-rw-r----- 1 oracle dba 5241856 May  8 10:37 kemsuat_1_655792404_95894.arc
-rw-r----- 1 oracle dba 5241856 May  8 11:06 kemsuat_1_655792404_95895.arc
-rw-r----- 1 oracle dba 5241856 May  8 11:37 kemsuat_1_655792404_95896.arc
-rw-r----- 1 oracle dba 5241856 May  8 12:15 kemsuat_1_655792404_95897.arc
-rw-r----- 1 oracle dba 5241856 May  8 12:52 kemsuat_1_655792404_95898.arc
-rw-r----- 1 oracle dba 5241856 May  8 13:22 kemsuat_1_655792404_95899.arc
-rw-r----- 1 oracle dba 5241344 May  8 14:01 kemsuat_1_655792404_95900.arc
Any idea why is this ?
  • 1. Re: Archived logs are 5MBish when the ORL is 10mb !
    FreddieEssex Pro
    Currently Being Moderated
    More than likely this is working as designed....

    Archived redolog is (significant) smaller than the redologfile. [ID 1356604.1]
  • 2. Re: Archived logs are 5MBish when the ORL is 10mb !
    Max Newbie
    Currently Being Moderated
    LOG_BUFFER is only 15 mb in this DB.Could this be the cause as suggested in the ML document ?
     
    SQL> show parameter log_buff
    
    NAME                 TYPE                 VALUE
    -------------------- -------------------- ------------------------------
    log_buffer           integer              15638720
    
    SQL > select 15638720/1024/1024 from dual;
    
    15638720/1024/1024
    ------------------
            14.9142456
    But LOG_BUFFER parameter is automatically set by oracle after some internal calculation. Right ? Something went wrong with that calculation ?
  • 3. Re: Archived logs are 5MBish when the ORL is 10mb !
    FreddieEssex Pro
    Currently Being Moderated
    I would doubt anything went wrong with the calculation. The document is explaining some of the factors which affect log switch frequency and one of those factors is the log_buffer.

    Why are you worried about this?

    I'd be more worried about the fact that you are having about 10 log switches in 1 minute. The rule of thumb is once every 20 minutes during a busy period.

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