Setup redologs
                                                 Last update (2008-02-20 20:30:42)
                                                                                                                   Date added (2008-02-12 13:12:40)

This article aims to help you how to setup the redolog groups. The main issues about the redologs are:
a)Where and how to store them?
b)How many groups to create?
c)How many members for each group?
d)How big must be each redolog file?

The answers
Because the answer in question c is the same for all database sizes (only 2, or at least 2) all the other questions basically depend on one hidden question. How big is your database?

LetĘs start with the obvious. Question a. Where and how to store them?
Store them in the faster available filesystems and also each redolog file member in different filesystem(the target is fast mirroring). For example for 3 groups one simple solution can be:
group1 member1=/filesystem01/log01a.LOG, member2=/filesystem02/log01b.LOG
group2 member1=/filesystem02/log02a.LOG, member2=/filesystem03/log02b.LOG
group3 member1=/filesystem03/log03a.LOG, member2=/filesystem02/log03b.LOG
They are spread in such a way that loosing one filesystem, still have one member from each group.
If you loose filesystem01, then you still have:
If you loose filesystem02, then you still have:
If you loose filesystem03, then you still have:
And at last about how many redolog groups and how big each member, we said: depends on the size of database. In a big database, a lot of changes happen during the day, so a lot of redo information is generating. In a small database, few changes happen, so small amounts of data stored in redologs.

100GB database-> 4 groups and each redolog file approx 400Mbytes
5TB database -> 10groups and each redolog file approx 1Gbytes

Tip: The frequency of switching redologs every day must be normal. If for example you have an average of 100 redolog switches per/day, to reduce it double the size of redolog files.

Other usefull links
Redologs information
Redologs switch calendar
Redologs add drop switch
Oracle DBA-> (147)
  Alertlog (3)
  Archivelog (5)
  Auditing (1)
  Backup - Recovery (19)
  Database files (6)
  Database options (2)
  DB links (2)
  Dependencies (1)
  Dictionary (2)
  Exp-Imp Datapump (6)
  Jobs (2)
  Mview (2)
  Networking (3)
  Objects (7)
  Parameters (2)
  Redologs (6)
  Roles - Grants (2)
  Rollback - Undo (8)
  Segments (3)
  Sequences (2)
  Sessions (14)
  SGA (14)
  Tables (10)
  Tablespaces (10)
  Temp (4)
  Toad (5)
  Transactions (1)
  Upgrade (2)
  Users (3)
Oracle APPS DBA-> (66)
Exadata (1)
Performance Tuning-> (59)
Oracle Real Cases (24)
Oracle Errors (23)
Oracle SQL tricks (32)
Oracle RAC (3)
Oracle Security (8)