Re: Anyway to estimate how much space flashback logs space will be needed in 11.2.0.4?

  • From: Mladen Gogala <gogala.mladen@xxxxxxxxx>
  • To: oracle-l@xxxxxxxxxxxxx
  • Date: Fri, 7 Jul 2017 07:47:53 -0400

On 07/06/2017 12:52 PM, Dba DBA wrote:

If I make a guaranteed restore point for a specific point in time. If the DB generates archivelog, is there a way to estimate how much space will be needed? We have limited space and may need to backout a build coming. The build includes a data migration. One option is to take a backout and restore from backup. The other options is a guaranteed restore point. The migration scripts are done by a whole other group. I have no idea how much archivelog will be generated.

Does more archivelog generate lead to more space needed for flashback logs for a single guaranteed restore point? Will my FRA fill up if I just have flashback database turned on? The archivelogs will get deleted at regular intervals. If we can use flashback DB, its alot easier and faster than restoring from backup.

Hi!

The simplest and the most accurate way of estimating this is figuring out the amount of daily change you will have in the database. Also, I really don't like the practice of keeping archive logs in the FRA. I prefer a separate directory and regularly scheduled archive log backups. What do you intend to do with flashback database? Do you intend to create any guaranteed restore points? Flashback writer writes all committed blocks to flashback logs, the "Core" book by Jonathan Lewis. You don't have control over the size of flashback logs. You can encounter flashback checkpoints and associated waits, which can be nasty if you have an application that uses a lot of NOCACHE CLOB fields. Your FRA should be large enough to hold all the changed data since the guaranteed restore point.

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Mladen Gogala
Oracle DBA
http://mgogala.freehostia.com

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