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Wednesday, July 2, 2008

FRA Capacity Planning

Kindly suggest some tips and how to determine my FRA?

First oracle recommended tip is to always keep yours FRA far away from yours Database location
possibly keep it at hard another hard drive, if possible keep this hard drive with separate
controller.

For FRA sizing decide how many days database backup you could maintain within Yours hard disk,
this could be determined by yours SLA ,usually there is maintained two days backup within hard
disk either it is FRA or non FRA,the rest of database backup as well current two days backup
should be transferred to tape cartridge. Typically what I do within my environment could be
helpful for you.

I keep at least last two current days backup for the entire database at hard hard disk within
FRA,beyond 2 days and these last two current days backup I move to tape cartridge, according to
business rule I maintain 30 tape cartridge for 30 days backup to revert back in case of any harm,
I rotate the same cartridge which lapse after 30 days.

i.e JAN tape1..tape30
    FEB tape1..tape30
    MAR tape1..tape30

You can dedicate yours FRA space by cheking yours database file size not with actual data by 

select sum(bytes) from v$datafile
/

Lets say if yours database file size about 80GB then you can either dedicate
2*80+20% extra for yours FRA.I maintain my retention policy for redundancy 2
days.After taking 3rd backup my first backup obsolete and before that any
archivelog also obsolete and can be reclaimable by deleting obsolete via RMAN.

For archivelogs pace you can observe 

select sum(blocks*block_size) archivebytes 
  from v$archived_log
where completion_time > sysdate-1 and status='A'

If you maintain yours archivelog within FRA then you also need to accomodate space for archivelog
within FRA,its recommended to put alls backup stuff within one single place which provide you FRA.

If you decide to put yours archivelog within FRA then yours estimation would 
become (2*80+archivebyte) x+20% x.

The above clue will determine you what should be the size of FRA.


Why last two current day’s backup should be at hard disk (FRA flash recovery Area) why not last
one current backup or why not last three current backup or why not last x backup or why is keep
backup at hard disk at all when I move it to tape cartridge, why to waste space when company
gives me tape cartridge space for each day backup?

the reason is that if you don’t keep any backup at hard disk then it will increase yours downtime
in case of hard disk failure or any failure which should not be for a good DBA,you will have to
have move last current backup from tape cartridge to hard disk (i.e. FRA) which will take x
hours/mins to be restored at hard disk (i.e.FRA), keeping at least one last current backup at
hard disk will save yours time from tape to hard disk. But if you keep 2 last current backup then
it would be safer in case of any mishap with last current backup, you will be able to restore
prior backup to last current one backup and then apply two days log for example

If you keep two last current backup at hard disk (FRA)

JAN 1
JAN 2
JAN 3<----------hard disk fail

You will restore Jan 2 backup but unfortunately yours 2nd Jan backup corrupted for any reason
then you can go with 1st Jan backup, you will restore 1st Jan backup apply archive log till
before the hard disk failure.


If you don’t keep last two backup just keep only last current backup ,in any case yours last
current backup corrupted then again you will have to have move last current backup from tape
cartridge to hard disk (i.e. FRA) which will take x hours/mins to be restored at hard disk (i.e.
FRA),if you came across that tape cartridge last current moved backup also not restorable from
tape cartridge then you will go with previous current backup and apply archivelogs till before
hard disk failure, think isn’t good if you save x hours/min to move backup from tape to hard disk
to make yourself and yours company downtime impact for the cost of purchasing more space for
backup.

Nevertheless if you can accommodate last 3 backups or more then that then I don’t think so there
is any harm but don’t rely at all at yours hard disk backup, move backup also to reliable tape
cartridge media.


Note : Above clue is not for flashback database technology.

4 comments:

Aman Sharma said...

Khurram,
Its not related to this post.Can you please post a blogpost regarding RMAN's Keep option in 10g,the option used for keeping the backup exempt for a longer period of time?
Cheers
Aman....

Khurram Siddiqui said...

Aman I will try my best and very soon i will post about RMAN's keep option.

Anonymous said...

It's Very nice.. Things which you have posted..!!

Pavan Kumar N

daspeac said...
This comment has been removed by a blog administrator.

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