Re: Archiver question

"Joel Garry" <joel-garry_at_home.com> a écrit dans le message de news:1113949946.550412.155090_at_f14g2000cwb.googlegroups.com...
| It doesn't. It is smart enough to parallelize and get part of the log
| from one member and part from the other!
|
| >From an old O7 faq:
|
| "Having multiple members to a logfile group is also advisable. If
| there
| are multiple members, all members in a group are used to perform the
| archive process. Assuming that there are three members, the first
| chunk
| is read from one of the members and is being written to the archive
| while
| reading a second chunk from second member, then a third chunk from
| third
| member, then back to first and the process continues in round robin
| fashion.
| If a corruption is found in one of the members, it is validated (read
| again)
| and if the corruption still exists, reading from that member is stopped
| and the rest are used.
|
| This is one of the big benefits of using multiple members instead of
| mirroring at o/s level. Oracle knows about the multiple members so it
| can
| optimize on archiving, but it does not know about the mirrors. One
| other big
| benefit with using multiple members is that a separate write is issued
| for
| each member, so the odds of having a totally corrupted redo log is
| diminished (corruption written to one mirror will usually propagate
| over to
| all other copies).
| "
|
| I have personally seen it figure out and overcome fairly severe
| corruption problems in recent versions, with no noticeable effect to
| users. But definitely check your alert log every day, there would have
| been a big effect one time if I hadn't noticed the messages about the
| failing hardware in time.
|
| jg
| --
| @home.com is bogus.
| ohnohackers!
| http://www.signonsandiego.com/uniontrib/20050418/news_lz1b18hacker.html
|

I just made a test with Oracle 9.2.0.4 on HP, 3 log groups with 2 members in each, 25 Mb size, 1 archiver. I "tusced" the archiver. The result is that arc always checks and opens all the members but reads only the first one of each group.
I can send the tusc output for each one that wants it but it is not difficult to reproduce the test.

Regards
Michel Cadot Received on Wed Apr 20 2005 - 10:32:58 CDT