RE: Common Oracle RDBMS Misconceptions

Good thread but I have not been following so I apologize if this was already said:

PCTINCREASE = 1

• Ethan

-----Original Message-----
Sent: Tuesday, June 26, 2001 5:51 PM
To: Multiple recipients of list ORACLE-L

Jeremiah,

Here's some more misconceptions for ya!:

• You *have* to take a COLD backup of the database after using resetlogs. (Not required - a Hot backup and archive logs is adequate. All hot backups / archive logs prior to that are invalid, though...)
• You *have* to create an additional Rollback segment in the SYSTEM tablespace before creating *any* object in a tablespace other than SYSTEM (even additional Rbs in a non-SYSTEM tablespace). This used to be true in V6 and before, not anymore.
• Backup the online redologs along with the datafiles/controlfiles in a Hot backup (Disaster strikes when the redologs are restored on the current online redo logs!!)
• Continuously run ALTER TABLESPACE COALESCE
• Allocate different values of INITIAL/NEXT extent sizes for large objects depending on the 'expected growth pattern' - this makes sure that the number of extents for large objects is kept down. (Sheesh!)
• COMPRESS=Y during Export compresses the extents into 1 huge extent, and that's GOOD!
• Make sure that all your Tablespaces have at least 15% (or whatever) free (i.e. stress the percentage rather than making sure that the largest free fragment is larger than the largest NEXT extent at the least)
• You are absolutely protected from Redolog file corruption by hardware multiplexing it. (i.e. What if you fat-fingered an online redolog?)

I might have added more on Tuning and Performance, but Gaja has already exploded all those myths!

One thing I will note though - there's bound to be lots of fire and flak erupting in your presentation. There are *lots* of so-called experienced DataBase Baby Sitters out there fed exclusively on 'Oracle for Dummies' books who had adopted these myths as reality and will be prepared to defend their position. You will need documented evidence in the form of logs or timings to make your stand for exploding some of these myths.

All the best!
John Kanagaraj

PS: On a related topic, I am unable to submit an abstract for OOW. Have been unable to do so for quite a while - spoke to Oracle, emailed 'em of no avail. Anyone else with the same story? (Or advice as to how this can be done?)

>-----Original Message-----
>From: Jeremiah Wilton [mailto:jwilton_at_speakeasy.net]
>Sent: Tuesday, June 26, 2001 10:05 AM
>To: Multiple recipients of list ORACLE-L
>Subject: Re: Common Oracle RDBMS Misconceptions
>
>
>All right folks, I'm collecting misconceptions, of the type
>held by newbies and
>oldtimers alike. My OOW proposal this year is for a
>presentation and paper on a
>whole laundry list of these things, similar to what I wrote
>for hot backup. I
>want to share what I have so far and solicit input for your
>favorites (pet
>peeves). I most certainly will credit individuals and this
>list for any ideas I
>glean.
>
>So far my favorite misconceptions are:
>
>* Hot backup stops writing to datafiles
>* All network communication is done through the listener
>* Always 'switch logfile' after (before, inbetween) hot backups
>* Media recovery is required if you crash during backup mode
>* Cold backup once a week ("just in case," "as a 'baseline'")
>* Export is a good way to back up your database
>* Shutdown abort is bad, crash recovery time is as long as
>'shutdown immediate'
>* Listener.log/alert.log clearing confusion
>* ORA-1555 can be solved by setting transaction (use specific
>rollback seg)
>* Big batch jobs should use one big RBS
>* ORA-600 means you have corruption / just call support for ORA-600
>* Lots of extents are bad
>* Databases can't be renamed
>* Select count (1) is better than count (*).
>* Listeners have to be started before the instance
>* NOLOGGING turns off logging for all operations
>* Oracle Corp. won't support NFS datafiles
>* checkpoint not complete - misguided solutions
>* Must reinstantiate standby after failover by recopying
>* redolog size change requires outage
>
>What's *your* pet misconception?
>
>--
>Jeremiah Wilton
>http://www.speakeasy.net/~jwilton
>
>On Tue, 26 Jun 2001, novicedba wrote:
>
>> I visited Jeremiah Wilton's web page
>http://www.speakeasy.net/~jwilton
>> I was shocked to read Hot
>backup mode explained
>> If this is true then I may be a victim of a disease called
>> 'Common Oracle RDBMS Misconceptions' . Somebody help me!!
>(Jim carrey-MASK style)
>> Please help me. If some one has few more articles like this
>enlighten me
>
>--
>Please see the official ORACLE-L FAQ: http://www.orafaq.com
>--
>Author: Jeremiah Wilton
> INET: jwilton_at_speakeasy.net
>
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: John Kanagaraj
  INET: john.kanagaraj_at_hds.com

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Author: Post, Ethan
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