Very Computer

In which state can/should the database be taken logical backups?
Open or Closed?

In other words, while the database is being accessed by users, can we
take logical backups?

Thanks in advance.

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Before you buy.

There's a discussion on this within the past day on this newsgroup.
Basically NO, unless you are in archivelog mode.

_______________
Jay M. Scheiner
Programmer/Analyst
Wolpoff & Abramson, LLP
remove _nospm_ from email address
Opinions are my own only!

Isn't logical backup simply export? You can always do it while the database
is being used. If you're concerned about exporting inconsistent data (data
are constantly being modified during the export process), add the parameter
consistent=y to exp.

Yong Huang

On 20-Jul-00 06:14:24, sfcheng said about Newbie Q: logical backup:

Quote:> In which state can/should the database be taken logical backups?
> Open or Closed?
> In other words, while the database is being accessed by users, can we
> take logical backups?

Yes you can, however, if you need a consistent logical backup, use "exp
consistent=y" or restrict the database.

Ewan.

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PGP footprint: 3A 82 19 D7 7A 61 D3 DC  4D F3 87 B2 27 99 BE 77

Yes, a logical backup is an export. And for that, the database must be
up and running. Another method to ensure consistency (if one is worried
about that) is to make sure that no one is on the system, place it in
restricted mode, export, and then disable the restricted mode.

HTH,
Brian

--
========================================
Brian Peasland
Raytheons Systems at
  USGS EROS Data Center
These opinions are my own and do not
necessarily reflect the opinions of my
company!
========================================

Well, if by 'logical backups' you mean run the export utility, then you have
no choice: the database MUST be fully open (because export needs to access
the tables, indexes and so forth).

If Users are allowed in during the export process (remember, you can
'startup restrict' to mean 'fully open but no ordinary members of the public
allowed in'), then you may wish to run export with a CONSISTENT=Y
setting -but prepare yourself first by having one hell of a rollback segment
ready to deal with the enormous quantity of read-consistent information that
will be generated and needed to make it work (if your exports start failing
with ORA-1555 Snapshot Too Old' error mesages, the lack of adequate rollback
segments will be the cause).

If you really meant 'physical backup', then backups can be taken at the
operating system level regardless of whether the database is opened or
closed, provided that, if open, you are running in archivelog mode, and
following the normal procedures (alter tablespace X begin backup; copy the
files associated with that tablespace; alter tablespace X end backup; now
repeat for tablespace Y and so on -i.e, one tablespace at a time).

Hope that helps
HJR

Quote:

> >Thanks in advance.

> >Sent via Deja.com http://www.deja.com/
> >Before you buy.

> _______________
> Jay M. Scheiner
> Programmer/Analyst
> Wolpoff & Abramson, LLP
> remove _nospm_ from email address
> Opinions are my own only!