RE: rollback segments during export

Think about it this way,

(Session 1)
SET TRANSACTION READ ONLY
Select * from emp;

22 rows selected.

(Session 2)
Delete from emp where dept = 20;

6 rows deleted.

Commit;

Commit complete.

(Session 1)
Select * from emp;

22 rows selected.

Export is the same as any other transaction, although unfortunately it does not show up in v$transaction (which I think it should).

Export will attempt to maintain read consistency throughout the life of the export cycle as well as throughout all the objects, although this isn't always possible (running out of RBS) and sometimes this process fails.

"Do not criticize someone until you walked a mile in their shoes, that way when you criticize them, you are a mile a way and have their shoes."

Christopher R. Spence
Oracle DBA
Phone: (978) 322-5744
Fax: (707) 885-2275

Fuelspot
73 Princeton Street
North, Chelmsford 01863  

-----Original Message-----
Sent: Monday, October 01, 2001 11:30 AM
To: Multiple recipients of list ORACLE-L

John,

You're making perfect sense, as that is the way I've always thought it worked. Based on some previous threads I read ( don't know if it was this list ) and ambiguous language in the docs, I'm not sure if it actually works that way.

Jared

On Monday 01 October 2001 00:50, John Kanagaraj wrote:
> Jared et al,
>
> My understanding could be flawed, but I think that setting 'CONSISTENT=Y'
> just adds a 'SET TRANSACTION READ ONLY' to the entire export process and
> thus ensures that all subsequent queries read all tables as of the time
the
> export started. Keep in mind that an export just does a 'select * from
> <table_after_table_after_table> along with a lot of other DDL generation.
> This is the reason you can expect ORA-01555 errors when trying to read
from
> a wrapped-around or shrunk rollback segment in the case a read-consistent
> read is required....
>
> I hope I am making sense here....
>
> John Kanagaraj
> Oracle Applications DBA
> DB Soft Inc
> Work : (408) 970 7002
>
> Listen to great, commercial-free christian music 24x7x365 at
> http://www.klove.com
>
> ** The opinions and facts contained in this message are entirely mine
> and do not reflect those of my employer or customers **
>
> >-----Original Message-----
>
> From: Jared Still [mailto:jkstill_at_cybcon.com]
>
> >Sent: Sunday, September 30, 2001 12:40 AM
> >To: Multiple recipients of list ORACLE-L
> >Subject: Re: rollback segments during export
> >
> >
> >
> >Chris,
> >
> >> Just because there is a PK/FK between tables, it does not
> >
> >mean they will be
> >
> >> exported in the same transaction. And thus, possibly out of sync.
> >
> >I didn't say there was. My implication was that your
> >tables would get out of sync. Setting 'consistent=y'
> >
> >won't prevent that:
> >: If you specify CONSISTENT=N (the default), each table is
> >
> >usually exported
> >
> >: in a single transaction. However, if a table contains nested
> >
> >tables, th
> >
> >Now it *could* be that I'm misreading the docs. It' been known
> >to happen, but that sentence says to me that each table is
> >exported as part of a single transaction.
> >
> >Anyone have proof to the contrary? The tech writer is being
> >rather ambigous, at least I think so.
> >
> >Jared
> >--
> >Please see the official ORACLE-L FAQ: http://www.orafaq.com
> >--
> >Author: Jared Still
> > INET: jkstill_at_cybcon.com
> >
> >Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: Jared Still
  INET: jkstill_at_cybcon.com

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-- 
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-- 
Author: Christopher Spence
  INET: cspence_at_FuelSpot.com

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