how to Mirror archive log
Fahd, December 02, 2020 - 7:33 am UTC
" Was it disk failure? If so, they should be mirrored "
electricity went down and server was powered off, that was what happened. after that one of the archive log went missing.
if i do Mirroring of archive log will it solve the problem ? how to Mirror ?
December 04, 2020 - 3:30 am UTC
Well....on power up, we don't need the *archive* log, just the redo logs for instance recovery.
And if the archivelog was incorrectly written to disk, then when you went to back it up with RMAN, I'm pretty sure it would have given you an error.
So I'm not entirely convinced the backup *frequency* here is the solution, but definitely you have the right philosophy of being very focussed on the integrity of your archive logs because obviously they are crtical.
Recovery on Power Off
A reader, December 05, 2020 - 12:33 pm UTC
"Well....on power up, we don't need the *archive* log, just the redo logs for instance recovery"
yes you are right, but i still don't fully understand how to recover from power failure, because i have faced this problem many times. and i still don't have a clear cut line of action to take after power failure. if you can give me some commands to start with, it will be a great help.
December 07, 2020 - 3:26 am UTC
You should *never* have to do a database recovery after a power failure because instance recovery is automatic.
If you *do* need to do a manual recovery, this is indicative of some potential issue with the integrity of the underlying storage on power loss. That is a big deal because if you can't have trust in your storage, then you can't have trust in your redo logs...
..which means you *will* one day day lose data, or worse.
Recovery after power failure
A reader, December 07, 2020 - 7:35 am UTC
"if you can't have trust in your storage, then you can't have trust in your redo logs..."
redo logs are multiplexed (3 copies) , so i think i can trust them, i have fully recovered the database from power failure many times, by doing following.
1) copying one of the redo log file and replacing with other two
2) RESTORE DATABASE
but some times i could not recover, and had to use imp/exp DMP files, so i don't fully understand, how to recover database from this situation.