Thanks, that’s great information. My log switching is all
over the place. Do I need to adjust my redo file size before
I enable archived mode? 97 switches in an hour seems quite a bit.
Well, I’ve had a look at your image and to be honest, your hourly average is between 3 and 5 most hours, with the off occasional 8 or 9 or, in one case, 12.
You are therefore switching every 12 - 20 minutes excluding the glitches. Looking further and where you highlight the 97 switches in one hour, the rest of that day is pretty low really.
Looking back over all the data, on occasions where you have a higher average than usual, I see a “surge” for about 1,2 or 3 hours - which to me implies a data load, or an import or a huge update, or similar.
I would tend to stick with it as it is at the moment, given the choice, but if I really had to make changes, I’d go for 1.5 - 2 times what you have now.
You cannot add a new logfile that is different sized by the way, you have to add new logfile groups and add the files to that. Every logfile in a group has to be the same size. So you would add in new ones, and when switched into, you can the drop the old ones.
One question, well two:
- How many logfiles do you have at present?
- How big?
The following will help:
select group# as log_group,
count(*) as members,
sum(bytes)/count(*)/1024/1024 as mb_each
group by group#;
Remember, when in archive log mode, the database will hang if an online redo log is filled and the system cannot switch to another because the other is still archiving.
I would advise at least three groups of two logfiles, hopefully, with each member logfile on a separate disc.
Contract Senior Oracle DBA
Capgemini Database Build Team
Internal : 7 28 2051
External : 0113 231 2051
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