RE: online redo log group switch

Quite correct, but I also would guess the original poster was wondering how they got in that order.

If you create all the online log groups at once, the order of use will make the rotation order of using the one holding the oldest first_change# match the group numbers. (Oldest first_change# must surrender to never been used and lowest creation datetime, or else you'd never use a new log group, right?)

If you drop and re-add, or just add an additional log group, then it goes into rotation after the current active group, ie. it starts getting used on the next switch. (And yes you can confuse the process if you start adding a new log group just before a switch, so that the new log group is not ready to use before the switch takes place. Last tested by me circa version 6, I suppose it could have changed, but pretending it hasn't doesn't affect the useful process flow.)

So if you're doing log maintenance and want to keep the rotation order obvious by name, you can switch log around so the highest numbered log is freshly active when you add the new ones. If you're operating at a change rate where ping-ponging the logs will accelerate throughput, then adding logs to the rotation at the right point is important. Otherwise, I think it is just convenient. I know I "like" it better when they switch in order from lowest to highest and then back to lowest.

Regards,

mwf
  -----Original Message-----
  From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Joseph Amalraj   Sent: Thursday, January 12, 2006 5:17 PM   To: roger_xu_at_dp7uptx.com; Oracle-L_at_Freelists. Org (E-mail)   Subject: Re: online redo log group switch

  It will go to the redo log holding the oldest first_change#

  Joseph Amalraj

  oracle-l-bounce_at_freelists.org wrote:
    Hi List,

    Why after Group 8, it goes to Group 2? I always thought it went to Group 1.

    Thanks,

    Roger

    SQL>select * from v$log;

--
http://www.freelists.org/webpage/oracle-l