> You can perform FBQ using RBSs, though this is probably not supported by
Oracle, so use it at your own peril. The chances of success are diminished
because of the difference in undo space
> management (rbs reuses space more often). I have done this several
times, but in a non-production environment.
Dan,
I'm sure you're aware of how to prevent RBS from ever wrapping.
So in theory, using FQB with standard RBS can provide snapshots
( excuse me, 'flashbacks' ) of data for an indefinite period of time.
You just need a lot of disk space. :)
Jared
"Daniel W. Fink" <[EMAIL PROTECTED]>
Sent by: [EMAIL PROTECTED]
06/06/2003 03:20 PM
Please respond to ORACLE-L
To: Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]>
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Subject: Re: A new form of ORA-1555
Mladen,
That is a common misconception, one that Oracle wholeheartedly
supports. Flashback Query (FBQ) depends upon the smon_scn_time table,
which is popluated in 9i, regardless of the undo_management setting. This
table is populated regardless of the UNDO_RETENTION parameter. This
parameter is the guideline (not absolute) that Oracle uses when deciding
which extents to reclaim when it needs space. If Oracle needs space, it
may take extents containing committed transaction info that is still
within the UNDO_RETENTION time.
You can perform FBQ using RBSs, though this is probably not supported
by Oracle, so use it at your own peril. The chances of success are
diminished because of the difference in undo space management (rbs reuses
space more often). I have done this several times, but in a non-production
environment.
IIRC, v$undostat is not populated unless the undo_management is set to
auto. This really does not help in making the transition from rbs to aum.
It would be nice to have it populated regardless so that you would have
data to use to set the undo tablespace size and the value of
UNDO_RETENTION.
I did make one mistake. You have to enable flashback for a table or
have the flashback_any_table privilege (Thanks, Kirti).
Dan
Gogala, Mladen wrote:
Flashback query is enabled by setting the UNDO_RETENTION parameter to the
desired number of seconds. Table V$UNDOSTAT contains the column
MAXQUERYLEN
which gives the max time that you can use to dynamically set
UNDO_RETENTION.
You also have to enable flashback for session using DBMS_FLASHBACK.
Mladen Gogala
Oracle DBA
Phone:(203) 459-6855
Email:[EMAIL PROTECTED]
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