We all know about the database block size. Remember db_block_size. But where the redo block size is defined.???

Answer is -> Redo block size is platform specific . It will the take the default value depending upon the operating system.

The easy way to find redo block size is to get trace of redolog and read that.

Below one is done on solaris platform:

1. Dump redolog:

SQL> ALTER SESSION SET EVENTS 'immediate trace name redohdr level 10';

Session altered.

2. Now check generated trace (it will under the same location where alert log is present)

cd /oracle/app/oracle/diag/rdbms/test1/TEST1/trace

cat TEST1_ora_26855.trc

LOG FILE #5:
  name #11: +REDOA/FMCPRE/ONLINELOG/group_5.256.943101611
  name #12: +REDOB/FMCPRE/ONLINELOG/group_5.256.943101623
Thread 1 redo log links: forward: 6 backward: 0
siz: 0xa00000 seq: 0x0000026e hws: 0x1 bsz: 512 nab: 0xffffffff flg: 0x8 dup: 2
Archive links: fwrd: 11 back: 0 Prev scn: 0x0000.130d0cab
Low scn: 0x0000.1334265f 12/13/2017 22:56:28
Next scn: 0xffff.ffffffff 01/01/1988 00:00:00
FILE HEADER:
        Compatibility Vsn = 202375680=0xc100200
        Db ID=444434112=0x1a7d86c0, Db Name='FMCPRE'
        Activation ID=444403392=0x1a7d0ec0
        Control Seq=250907=0x3d41b, File size=10485760=0xa00000
        File Number=5, Blksiz=512, File Type=2 LOG --------------->>>>>>>>>>>>>>>>>>  check the blksiz
Format ID is 242

Now here check the value of Blksiz , here it is 512 i.e 512 bytes.

So redolog block size in this database is of 512 bytes.