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Re: Whats Fuzzy in v$datafile_header

From: <Kenneth>
Date: Wed, 15 Feb 2006 15:41:50 GMT
Message-ID: <43f348b1.1063187@news.inet.tele.dk>


On 14 Feb 2006 22:47:29 -0800, "jackal" <jackal_on_work_at_yahoo.com> wrote:

>Hi,
> I have a db in which all tablespaces are ONLINE. I ve not issued
>ALTER TABLESPACE BEGIN BACKUP command on any of the tablespaces. But
>still when i query the v$datafile_header table i get a YES value in the
>FUZZY column for all datafiles.
>
> Is there something wrong with the datafiles?
>
>Thanks in advance
>Jackal
>

I believe that the FUZZY column will only display "NO" when Oracle is absolutely sure that the filet is consistent, that is, it has been completely checkpointed and verified as such. Which means that any online datafile will display "YES" in that column :

SQL> startup mount;
ORACLE-instans er startet.

Total System Global Area 101785428 bytes

Fixed Size                   454484 bytes
Variable Size              75497472 bytes
Database Buffers           25165824 bytes
Redo Buffers                 667648 bytes
Database er monteret.
SQL>
SQL> select fuzzy from v$datafile_header;

FUZ

---
NO
NO
NO


SQL> alter database open;
Database er µndret.

SQL> select fuzzy from v$datafile_header;

FUZ
---
YES
YES
YES


So opening the datafiles for transactions will mark the datafiles
"FUZZY"..

When opening the database read only, Oracle knows that the datafiles
are consisten and can't be written to, so :
 
SQL> startup mount;
ORACLE-instans er startet.

Total System Global Area  101785428 bytes
Fixed Size                   454484 bytes
Variable Size              75497472 bytes
Database Buffers           25165824 bytes
Redo Buffers                 667648 bytes
Database er monteret.
SQL> alter database open read only;

Database er µndret.

SQL> select fuzzy from v$datafile_header;

FUZ
---
NO
NO
NO

However, if you "shutdown abort" from an open read/write database,
oracle has not made instance recovery before shutdown and cannot
ensure consistency , thus :

SQL> shutdown abort;
ORACLE-instans er lukket ned.
SQL> startup mount;
ORACLE-instans er startet.

Total System Global Area  101785428 bytes
Fixed Size                   454484 bytes
Variable Size              75497472 bytes
Database Buffers           25165824 bytes
Redo Buffers                 667648 bytes
Database er monteret.
SQL> select fuzzy from v$datafile_header;

FUZ
---
YES
YES
YES

Here the datafiles are recorded as fuzzy even i mount mode. When you
open the database, instance recovery will be made, and when you
shutdown (not abort)  and mount it, the FUZZY column will show "NO"
again.

- Kenneth Koenraadt
Received on Wed Feb 15 2006 - 09:41:50 CST

Original text of this message

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