How about downtime when you upgrade your Oracle Database with Data Guard?
Short answer: You should expect slightly more downtime. Unless you head into a rolling upgrade.
How Long Does An Upgrade Take?
If I had a dime for every time someone asked me this question, I would have bought a tractor, retired, and worked full-time at our farm.
My boss, Mike, created a long blog post about it without giving a real answer. If he can’t estimate it, no one can!
But I will give it a try anyway. A ballpark figure is 15-45 minutes for the actual upgrade. Then add all the extra stuff that surrounds the upgrade.
Does Data Guard Change That?
Yes, it does. Extra downtime is needed.
You don’t add any extra time to the actual upgrade of the primary database. During the upgrade, redo transport is on, and the primary database ships redo to the standby database, but it has no significant impact on the duration of the upgrade.
But you do need a little extra time before and after the upgrade.
| Primary | Standby | Added Time |
|---|---|---|
| Restart Data Guard in new Oracle Home | 5 min | |
| Upgrade primary database | ||
| Verify standby has applied all redo | 2 min | |
| Optionally, test a switchover | 5 min | |
| TOTAL 7-12 min |
If you follow the standby offline approach, you need more downtime. In that approach, you keep the standby database offline during the entire upgrade, and it needs time to catch up afterward. I would estimate it adds 5 min of extra downtime, totaling 12-17 min instead.
This is the best you can do with a physical standby database. But …
Rolling Upgrades
If you want to upgrade with almost no downtime at all, you can do rolling upgrades. A rolling upgrade uses DBMS_ROLLING to reduce the downtime for an upgrade to the time it takes to perform a regular switchover.
Under the hood, a rolling upgrade uses Data Guard as well. This blog post series is about upgrading with physical standby databases, but a rolling upgrade requires a logical standby database. It’s out of scope for this blog post series.
Why don’t we all do rolling upgrades?
- A logical standby database has more restrictions than a physical one.
- A logical standby database uses SQL apply instead of redo apply. SQL apply is not as efficient as redo apply and can become a performance bottleneck.
- It’s more complicated.
But rolling upgrades are really cool, as you will see in this demo.
You can find more details in our webinar How Low Can You Go? Zero Downtime Operations. Slides and recording is available on demand.
Databases Are Fun 
Hi Daniel. Nice Blogpost one more time.
Btw. Do you have a blog one relate to use DG as a performing upgrade strategy. Means create a DG in 19c from a DB in 12.1 for example. Mix version.
Thanks in advance
Best Regards
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Hi,
You can only mix database releases with Data Guard when you use a logical standby database. When doing so, you can benefit from rolling upgrades and DBMS_ROLLING package (the latter requiring Active Data Guard). I don’t have a blog post series on rolling upgrades (yet, perhaps), but we do have a few good YouTube videos.
I hope that helps,
Daniel
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