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Video : Flashback Version Query

Today’s video gives a quick run through of flashback version query.

If you prefer to read articles, rather than watch videos, you might be interested in these.

Video : Flashback Query

Today’s video is a quick demo of flashback query.

If you prefer to read articles, rather than watch videos, you might be interested in these articles.

Result Cache 2

Following on from my earlier posting of problems with temporary table and the PL/SQL result cache (a combination which the manuals warn you against) here’s another problem – again, to a large degree, self-inflicted.

Imagine you have a complex report involving a large number of financial transactions with a need to include calculations about current exchange rates. Unfortunately the rules about calculating the appropriate exchange rate for any transaction are complex and you find you have a choice between adding 6 tables with outer joins and a couple of aggregate (max) subqueries to the base query or calling a PL/SQL function to calculate the exchange rate for each row. I’m going to create an extremely simplified model of this requirement:

Flashback Logging

One of the waits that is specific to ASSM (automatic segment space management) is the “enq: FB – contention” wait. You find that the “FB” enqueue has the following description and wait information when you query v$lock_type, and v$event_name:

Don't delete your flashback logs manually

What happen when someone will delete Oracle flashback logs ? You probably don't notice it until you will try to flashback database or bounce instance. 
There is no hope for flashback database without flashback files but there is still way to start your database again without recovery or data loss.

Here is a scenario:
[oracle@dev-6 alert]$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.4.0 Production on Tue Jul 1 09:34:18 2014

Copyright (c) 1982, 2013, Oracle. All rights reserved.


Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production

Don't delete your flashback logs manually

What happen when someone will delete Oracle flashback logs ? You probably don't notice it until you will try to flashback database or bounce instance. 
There is no hope for flashback database without flashback files but there is still way to start your database again without recovery or data loss.

Here is a scenario:
[oracle@dev-6 alert]$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.4.0 Production on Tue Jul 1 09:34:18 2014

Copyright (c) 1982, 2013, Oracle. All rights reserved.


Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production

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