Oracle数据库中，redo文件的block大小（blocksize）是跟平台相关的，因此redo文件的block size是无法改变的

至于如何查看redo文件的blocksize，有两种方法：
1.直接查询v$log视图
在Oracle 11g之后，可以直接通过查询v$log.blocksize就可以查到
如下：

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SQL> select * from v$log;
GROUP# THREAD# SEQUENCE# BYTES BLOCKSIZE MEMBERS ARC STATUS FIRST_CHANGE# FIRST_TIM NEXT_CHANGE# NEXT_TIME
---------- ---------- ---------- ---------- ---------- ---------- --- ---------------- ------------- --------- ------------ ---------
1 1 289 52428800 512 1 YES INACTIVE 2686107 30-JUL-16 2706826 30-JUL-16
2 1 290 52428800 512 1 YES INACTIVE 2706826 30-JUL-16 2727425 30-JUL-16
3 1 291 52428800 512 1 NO CURRENT 2727425 30-JUL-16 2.8147E+14

可以看到Linux平台下的BLOCKSIZE为512

2.dump logfile查看blocksize大小
方法如下：
a. ALTER SESSION SET EVENTS 'immediate trace name redohdr level 10';
b.在udump目录下查看相应的trc文件
c.在trc文件中找“bsz=”内容，即是redolog文件的blocksize

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*** 2016-07-31 07:35:36.164
DUMP OF LOG FILES: 3 logs in database
LOG FILE #1:
name #3: /home/oracle/app/oracle/oradata/orcl/redo01.log
Thread 1 redo log links: forward: 2 backward: 0
siz: 0x19000 seq: 0x00000121 hws: 0x7 bsz: 512 nab: 0x1d0 flg: 0x1 dup: 1
Archive links: fwrd: 0 back: 0 Prev scn: 0x0000.0028ac04
Low scn: 0x0000.0028fc9b 07/30/2016 20:46:26
Next scn: 0x0000.00294d8a 07/30/2016 20:49:40
FILE HEADER:
Compatibility Vsn = 186647552=0xb200400
Db ID=1434730535=0x55844027, Db Name='ORCL'
Activation ID=1434687783=0x55839927
Control Seq=6323=0x18b3, File size=102400=0x19000
File Number=1, Blksiz=512, File Type=2 LOG
Format ID is 2
redo log key is 214e32a54a14bea8f0de67f8c53a9f
redo log key flag is 5
descrip:"Thread 0001, Seq# 0000000289, SCN 0x00000028fc9b-0x000000294d8a"
thread: 1 nab: 0x1d0 seq: 0x00000121 hws: 0x7 eot: 0 dis: 0
reset logs count: 0x360ef4a8 scn: 0x0000.000e2006
Low scn: 0x0000.0028fc9b 07/30/2016 20:46:26
Next scn: 0x0000.00294d8a 07/30/2016 20:49:40
Enabled scn: 0x0000.000e2006 03/20/2016 02:30:00
Thread closed scn: 0x0000.00294d88 07/30/2016 20:49:25
Disk cksum: 0x2d4 Calc cksum: 0x2d4
Terminal Recovery Stop scn: 0x0000.00000000
Terminal Recovery Stamp 01/01/1988 00:00:00
Most recent redo scn: 0x0000.00000000
Largest LWN: 0 blocks
Miscellaneous flags: 0x800000
Thread internal enable indicator: thr: 0, seq: 0 scn: 0x0000.00000000
Zero blocks: 8
Enabled redo threads: 1
LOG FILE #2:
name #2: /home/oracle/app/oracle/oradata/orcl/redo02.log

如上所示，blocksize为512

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oracle数据库redo文件的blocksize

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