Re: Rman Explanation Please

On Jul 31, 8:42 am, artme...@xxxxxxxxx wrote:
On Jul 30, 6:02 pm, Palooka <nob...@xxxxxxxxxxx> wrote:





artme...@xxxxxxxxx wrote:
Hi,

We just implemented RMAN and were reading the documentation and came
across this:

"For example, you can implement a three-level backup scheme so that a
full or level 0 backup is taken monthly, a cumulative level 1 is taken
weekly, and a differential level 1 is taken daily. In this scheme, you
never have to apply more than a day's worth of redo for complete
recovery."

We;re trying to understand that.  The monthly level 0 is obviously a
full database backup.  We do not understand the difference between the
cumulative level 1 and the differential level 1 if both seem to use
the monthly 0 as a source.

How does that all fit into only needing 1 days worth of logs??

Thanks all, we all appreciate it.

In principle, if you have your level 0 backup available, plus all your
incrementals, you can apply them all, and only need your logs since the
last incremental backup. But if it's the wrong day you might need to
restore 8 backups, plus apply today's redo.

Instictively I prefer cumulative incremental backups if it is feasible.
That way, you only need to restore one full backup, one cumulative
incremental, then apply archive logs since the last backup and the
online redo.

Palooka

Palooka,

So, you may suggest a weekly level 0 incremental backup, backs up the
entire database.  Then after that, cumulative level 0 backups for the
rest of the week.  Should a restore be needed, then restore the level
0 incremental, then the level 0 cumulative, then archive
logs......correct?

Seems simple enough....

Thank you.

Um, doesn't the level 0 incremental have all blocks?

You probably meant to say cumulative level 1 daily.

The incremental stuff is a trade-off for places that have too many
changes to keep an incremental every day.

Not that I've ever tried it, just reading the docs. I've enough
horsepower and disk to do a full every day. Getting it offnode is
another issue, so I might start. But that depends on management,
which is a more difficult problem.

jg
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