LOG_ARCHIVE_DEST_n > 1

[khussain]

When this param (LOG_ARCHIVE_DEST_n ) is used to specify more than one destination, are the arch logs written to the mount point destinations sequentially ?

Meaning, once the first destination is filled up, the arch logs will be written to the second dest., and then after the second is filled up try the first dest. again ???

[Halo]

The arch files are written to the destinations in parallel (simultaneously). If the first arch destination gets filled, it'll write to the second destination, if it cannot write to either destinations, the instance will fail.

[khussain]

So why is this parallel, when LOG_ARCHIVE_DEST_2 will be written to only when LOG_ARCHIVE_DEST_1 is filled up ? Isn't this in sequence _1 then _2 then _1 again ... ???

[khussain]

Anyone else know anything about this ?

[sambavan]

Halo is correct. The multiple destinations are used in the archive , as to multiplex the archiving processes. The process is done in parallel and the possiblility that it could fail when the first dest. gets filled depends on setting MANDETORY or OPTIONAL. If one destination gets filled up, then the archiver continues with the other untill that destin gets filled.

Answering to the delima, when I say parallel, it mean that when the files are written to dest 1, they are also written to destin 2. This would really become helpfull in the case if you are setting up a standby database.

As,

---> arch_1_593.arc at DEST 1
|
log52---
|
---> arch_2_593.arc at DEST 2

I hope this would help you to undestand the concept.

Sam

[khussain]

Thanks Sam, I have another question after reading your explaination:

When there are multiple LOG_ARCHIVE_DEST_n specified, does that mean that they will get multiplexed, or that the destination will form a pool of mount points for the arch. logs ???

After reading the doc. (http://technet.oracle.com/docs/products/oracle8i/doc_index.htm), it seems that this parm "LOG_ARCHIVE_DUPLEX_DEST=" is used for multiplexing.

In either case, I would like to assign 2 mount points for arch logs, in case one fills up, the archiever should create arch files in the second location, NOT MUTIPLEX them.

Thanks.

[sambavan]

So far to my knowledge, oracle hasn't come up with the automatic switching machenism as you want. But there is a feature that you could use to switch between the destination.

i.e
log_archive_dest_state_2 = DEFER
log_archive_dest_state_3 = DEFER

by default it is ENABLE.

ALTER SYSTEM SET log_archive_dest_state_3 = ENABLE

Archiving is not performed when the stat is DEFER and this could help you. You could write an cron job to monitor the filling of one destination and then switch the archiving to the second and deffer the first.

On the other hand, the methods I specified earlier are of multiplexing and not of the order that you want it to be. But you can make them function like you wanted to be setting up the above stated parameters and alter them dynamically.

Sam

[khussain]

Thanks again buddy.

I just thought of something, I will leave it to just one dest., and write a shell script to move some files to another location if arch dest mount point is > n%. And CRON that for every hour.

That's it - shell scripts RULE !!!

[sambavan]

You bet it is. BTW, when you do some recovery, then you have to mv/cp all the archive files back. If you were to set the destination and go by the method said earlier, oracle, will figure out what to read from where. That is one of the advantages.

Good luck
Sam

[khussain]

10-4 Buddy !!!
Over and Out.