after migration to oracle9i from informix we had 80 GB index and 40 GB data.we created 5x500 MB redo log files(total 2.5 GB),2x20 GB undo fies,1x10 GB system tablespace file,1x30 GB temp file.we are using Baan IV ERP.

we want to do online backup.we are using db in NOARCHIVELOG mode. how much space we need for online backup.should we turn the db to ARCHIVELOG mode to do it? we have 20 GB file system for Archive Logs, and redo logs switch occurs at about 10 minutes.what happens if our Archive Log space fills up? when it occurs db hangs up?

Thanks in advance.

I am not sure about Oracle 9i, but it should be the same
as 8i.

For starters you will need to change the database
to archivelog mode. When running archivelog mode and the
directory where the logs are written too becomes full the
database will not be able to do any updates and hang until
there is free space. This should only happen after all
the redo logs have been filled.

To work out how much space you will need for the archive log
directory --- determine how many log switches occure during
the time period you plan to keen the archive log online, then
multiply this by the redo log size. Don't forget you can
backup the archive to tape every few hours.

Hi Beksalur,

Why Archive mode?

If you want to take oracle online backup, your database should be in ARCHIVELOG mode. Please Note >> Most Oracle production databases are run in ARCHIVELOG mode. You'll hear that term a lot, so you need to know just what it means. ARCHIVELOG mode is what enables you to recover from a failure without losing any transactions that were committed prior to the time when the failure occurred. In the real world, this is almost always a requirement. Depends on how much data you can afford to loose, and how much downtime you can afford (daily cold backups?).
ARCHIVELOG mode is a mode wherein a copy is made of each redo log file before the log writer process reuses it.

How much space required?

For taking online backup (Hot Backup) you need space equals to your database size (it is copying of database in fuzzy mode).

I am not undestood, if your database is in NOARCHIVELOG mode, Why you wrote, "we have 20 GB file system for Archive Logs."

Just Curious.

-Suhas

we havent swithed our new server to produnction db yet.our migration havent completed. after we import our old informix data ,we see that we got 60 GB data,80 GB index,total of 140 oracle data.in test mode we use oracle at NOARCHIVEMODE. after migration we begin to use it at ARCHIVEMODE.

so i want to find answers the following questions:

1)must i find a 140 GB file space in the filesystem if i want to do backup in online mode?
2)can i take the online backup to tape?(our tape drive is IBM LTO2
with capacity of 200 GB at uncompressed mode)?
3)our oracle transactions consumes 500 MB redo log in half hour.how can i manage the space reserved for archive logs,which at capacity of 40GB. when i can delete the old archive logs,after taking online backup?

Thanks for your interests.

You don't need file system space for an online backup if you do it to tape. Your hardware should be fine. It all depends on what backup program you use and whether it can interface with the Oracle RMAN backup/restore manager and your tape drive.

The same applies for archive logs. I would set up a backup that kicks off once your archivelog file system runs over e.g. 70% of used space. If the backup is succesful you can have RMAN delete the archive log files and you will be back to 0%

should i take online backup to tape with tar command?so that when need restoring i can easily extract it with tar -xvf dev/rmt/..

As an alternative approach for you to consider.

We now have LTO tape drives which are fairly reliable, however we used to have 8mm which were very limited capacty and also unreliable.

The approcah that we use is to do unattended backups overnight. As each table space is backed up to disk, we compress the files using unix 'compress'. Our archive logs are compresses throughout the day. After the oracle backup steps are finished we 'tar' to tape.

This way we don't need as much intermediate disk space to hold the backup and we can re-run the actual transfer to tape if there is any tape problems (dirty tape, tape used to many tiems, tape hardware glitch etc).

For the actual oracle tablespace backup we use 'alter tablespace xxx begin/end backup'.

Terry

I was assuming you were using a backup program with specific oracle features. If you are stuck with 'tar' then you can go with what Terry has said.