hotbackup archivelog required?

[khoshtip_uk]

HI,
why do we have to backup archive log file for hot backup ? doesnt data file conain those changs?
how do we know which log files to backup ?oldest sequence number ?just cant get my around it

if it happend to restore/ recover database will we be aplying those archive logs which backed up with database or the one currently in place ?

if we have a backup from yesterday but archive log for past 5days,can we restore using the backup and roll back database to as it was 4 days ago for example ?

[PAVB]

You have to read a lot more about how backup works.

Just a tip: If your backup/recovery strategy calls for point-in-time recovery you have to resort to hot backup which requires archive logs to be backup too... assuming you might want to restore it some time in the future

Remember, hot backups are not consistent, that's why you have to apply logs until reaching a consistent point in the future.

[khoshtip_uk]

You have to read a lot more about how backup works.

.

good point !
where for example? any link ?
I think i need to know how things works rather than knowing how to technically perform backup etc...

[PAVB]

Just google it... kinda "oracle hot backup" and you will get some good entries like...

http://webhost1.njit.edu/~hoskins/or...up-hoskins.pdf
http://orafaq.com/faqdbabr.htm

Hope this helps a little

[khoshtip_uk]

I have gone through both links just today lol,

I think if I could find out answer to the following questions then I will be fine,

lets say we have a database created 2days ago(thursday) and performing one hot backup including archive log everyday,

1. ist required to back all available archive logs every day while performing oracle hot backup or just certain one ?if certain ones then how do we figure out which one to backup and how and why?

2. lets say 20 days down the line we loss one data file. we have archive log file only for past 4days and last backup was performed 7 days ago ! will we be able to restore and recover database? or not (because of lost archive log in between? last backup date&oldest archivelog.

4. am im right to say that if we have a hot backup for day 1,2,3,4,10,11,12,....20 with full archive log since day first and want to restore to day 7 its possible to restore backup day 18 as an example and recover do incomplete recovery untill date of day 7 ?

[PAVB]

1-- You want to backup all archive logs generated after the moment you initiate a Hot Backup

2-- No, you don't because in your scenario you are lacking archive logs generated immediately after the Hot Backup was taken

4(?) -- If you want to do point-in-time recovery until Day 7 in your scenario want to restore Day 4 Hot Backup and roll forward archive logs until reaching a consistent point in time around your target hour in Day 7

[khoshtip_uk]

thanks for your reply I undrestand it all now. its all clear...
just question number 4: you mean this is the only possible solution ? means if we we havent go backup for day ,1,2,3,4 then will not be able to do incomplete recovery to date 7 ?

thanks

[PAVB]

in your scenario only backup set that matters is:

1- Day 4 Hot Backup
2- Arquive logs generated from start of Day 4 Hot Backup until target recovery point.

[khoshtip_uk]

got my head around it thanks

[mrchrispy]

build a server and have a play - it really helps.