Re: backing-up with rman and expdump

On May 10, 7:03 am, Joe <joe1..._at_tlen.pl> wrote:
> On May 10, 12:59 am, sybra..._at_hccnet.nl wrote:
>
> > expdmp is a logical backup. Nothing more than a series of insert
> > statements. So importing doesn't guarantee all records return to their
> > original locations. Consequently you won't be able to recover the
> > database (= apply (archived) redologs) after impdmp.
> > You don't make an expdmp every 2 minutes, do you?
>
> I do expdmp 2 times a day, noon and evening, after 6pm.
> I know I wont be able to use redologs.
> Why would my records not get to the right place, just like they were
> before?
> i do not have stored procedure in db.

You really need to read the backup and recovery basics manual. There you find things like this, right at the beginning:

"Physical backups are the foundation of any sound backup and recovery strategy. Logical backups are a useful supplement to physical backups in many circumstances but are not sufficient protection against data loss without physical backups."

Now, what they might mean here is not losing any transactional data, and for your organization it may seem sufficient if they "only" lose half a days work. (From what I've seen, such a judgment usually comes from faulty risk analysis.)

But...

What is also implicit is that you need redundancy in any recovery plan. You need to remember, any given backup, logical or physical, may be unusable for a variety of reasons. With a logical backup, if one is bad, you can only go to the previous. If that one is bad, the one before that. And so on until you realize you are TSOL. With physical backups, it is possible to have multiple copies of archived logs in various backups (as well as online), so it may be possible to go to an earlier backup and apply logs as much as desired. In addition, as others have alluded to, RMAN has additional capabilities for corruption detection and repair. Beyond that, there are newer features based on archive logging that allow recovery without even bothering with the backups. There is also the occasional glitch doing an import.

The logical backups are really for moving data around (that would explain the data pump name, right?), and in some cases recover some data from a previous time. They are not designed to be depended on as a database backup. We can't be any clearer than that: read the manuals.

That said, I use exp/imp all the time for various things, it is very useful to have recent exports as a matter of course. It's just not for primary backup purposes. You might also be taking note of any effects on your undo if you are exporting during transactional time.

jg

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