Re: training for new DBA's
- From: Hans Forbrich <fuzzy.graybeard@xxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Mon, 10 Feb 2014 14:56:14 -0700
On 10/02/2014 12:47 PM, Mark Bobak wrote:
³ŠBack up the redo logsŠ²
Um, you¹re referring to *online* redo logs? If you¹ve properly
implemented your backup strategy, there should never be a need to backup
the online redo logs. Tools like RMAN won¹t let you back them up.
Can you explain more?
When I teach the B&R or Basic DBA courses, I get my students to 'swear
(on a stack of Gummy Bears)' that they will
a) Never Back up the Redo Logs, and
b) Before starting a recovery, they will take a safety COPY (but not
back up) of the existing Redo Logs so they can restart a recovery if
they botch the steps.
I then go on to highlight some cases, and emphasize that more DBAs have
been fired for violating these two points than any other reason (of
which I am aware). 9 Well, they were not fired for violating the points,
but for getting the recovery into an unmanageable and unrecoverable
state, and having no plan B since they overwrote their Redo Logs with
old copies.
With other teams "knowing better than the DBA" about what backups are
required thus avoiding RMAN, and doing things like BCV splits and
shoosting the mirror off to tape, it is highly likely that a) gets
violated at some point.
The differences between a) and b) are:
a) Is an automated situation, and it is very very likely that a restore
will bring back an old set of Redo Logs if they were backed up in the
first place;
a) Also often involves the backup and restore team, increasing the
possibility of that Redo Log overrwrite in the previous statement;
The restore from a) is done under duress and with too many dragons
breathing down the DBA's neck;
A Safety Copy in b) is tucked away in the DBA's home directory or some
other non-traditional place;
That Safety Copy should not be used, or required, unless the world has
gone TU
/Hans
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