Alejandro Vargas' Blog

  • October 8, 2007

Oracle Flashback Technologies

Alejandro Vargas
Technical Leader, ACS Global Delivery, Infrastructure & BigData

Flashback Database, Table, Query, Transaction and Drop provides an extremely useful set of tools to the DBA.  Once understood they are easily configured, implemented and used, in case of need.

They are not only useful for recovery purposes but sometimes for informational purposes as well, a question like: which was the value for some record the last 6 hours? can be easily answered using flashback records.

Metalink Note 435998.1 : What Do All 10g Flashback Features Rely on and what are their Limitations ? contain additional conceptual information and links to some of the sources I did use to prepare the document I'm attaching here:

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Comments ( 2 )
  • Bob McAusland Thursday, October 11, 2007
    The only issue I had when evaluating Flashback, was the additional I/O generated. When we set up our 10g system, using a NetApp Filer as the central storage on a 2-Node RAC on Solaris 10 , inserts were taking twice the time with flashback on. As we wanted to maxismise throughput, we did not use Flashback.
    I'd appreciate any thoughts on this.
  • Alejandro Vargas Monday, October 29, 2007
    Flashback need to write flashback logs to some destination that you need to define, nevertheless the flashback logs are not as critical they need to be located on disk performing as well as the database datafiles disks.
    You can also enable trace with event 10046 level 12 to see which is the difference in terms of waits, it should be some overhead because you are doing more IO but 50% seems to be too much
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