Oracle 11G - SE1 Flashback Query Retention Log

Question

I want to increase the size of the FLASHBACK "retention log" so I can do flashback queries far back in time ( from now on ). How do I do this ? I'm using Oracle 11G SE1 on Amazon RDS.

Cheers !

Answer 1

If you're looking at doing flashback queries (SELECT * FROM EMP AS OF...), then the limiting factor is how big your UNDO tablespace is, what your UNDO_RETENTION is set to, and how quickly your application generates UNDO. The UNDO tablespace, though, will always be limited in size and will always be subject to pressure to purge data before your UNDO_RETENTION has been exceeded (unless you want the application to stop at that point but that is seldom a useful option). That means that the length of time that you can retain data in UNDO is going to be limited. If you're really aggressive, you might get a couple of days under optimal conditions. Most systems, realistically, can flashback a few hours at most.

If your idea of "far back in time" is more than a day or two, you're probably looking at the wrong technical solution to whatever business problem you have and you probably want to look at alternate approaches. If you can explain the business problem, we can probably assist in coming up with alternate technical solutions.