Category Archives: Redo

Private Redo Thread

The “in memory undo” buffer is actually a buffer for the redo that describes the changes to the undo.

If you look at x$kcrfstrand you can see some information about redo threads (buffers), both public and private. In the example below I have 2 public threads and 10 private threads, but four of the private threads have been dynamically disabled so only 6 of the private threads are showing a buffer address.

select indx,
       ptr_kcrf_pvt_strand,
       strand_size_kcrfa
  from x$kcrfstrand;
      INDX PTR_KCRF STRAND_SIZE_KCRFA
---------- -------- -----------------
         0 00                 3494400   public
         1 00                 3494400
         2 20F27C80             66560   private
         3 20F38080             66560  
         4 20F48480             66560
         5 20F58880             66560
         6 20F68C80             66560
         7 20F79080             66560
         8 00                   66560   dynamically disabled
         9 00                   66560
        10 00                   66560
        11 00                   66560