Hello and welcome to the SAP HANA Academy.
The topic of this video tutorial series is SAP HANA 2.0 SPS 03, What’s New?
And in this video we will take a look at the new system administration feature: fallback snapshot.
Hi, I am Denys van Kempen.
Now, you might be tempted to think that we are talking database backup and recovery here,
Fallback snapshot, sounds a lot like data snapshot, what we called storage snapshot before,
and it is true, the technology is very similar but not the use case.
First of all, you can only create fallback snapshots for tenant databases, not for the system database,
and you can only create a single fallback snapshot.
If you want to create a new one you have to delete the old one first
and that is pretty much the whole point.
You would use a fallback snapshot to quickly return a particular tenant database to a previous state.
When would you want to do that?
Well, for example, for training databases.
At the end of the training session, just reset the database to the original state.
So, how does it work?
I am connected here with the SAP HANA cockpit to the system database.
For tenant management, click the Overall Tenant Statuses tile.
This will open Manage Databases.
Then, select the tenant anywhere in the row and then from the header menu, click the ellipsis
and select Create Fallback Snapshot.
This will create a snapshot for us and like the name suggest this takes a fraction of a second to complete
and when done, the snapshot will appear with its timestamp in the Fallback Snapshot column.
Also note that, in the system database row, the entry is Not supported.
Then, after a hard day of training, you want to reset the tenant database.
Go back to the same context menu and this time select Reset to Fallback Snapshot.
We will get a nice little warning.
Tenant T01 will be reset to the state as of ‘time stamp’.
Tenant will be stopped immediately.
Do you want to continue?
Well, yes. Stop & Reset.
The tenant database will be stopped and then started from the snapshot.
This takes a bit of time, the time to restart a tenant database, basically.
I will fast-forward that a bit for you.
Then, should you no longer need your snapshot - you probably already noticed - just select
Delete Fallback Snapshot from the menu.
Again, you will be prompted.
Do you really want to?
Yes - and the snapshot is gone.
Here we have the SQL
ALTER DATABASE database name CREATE FALLBACK SNAPSHOT
creates the snapshot
ALTER SYSTEM START DATABASE database name FROM FALLBACK SNAPSHOT
returns the database to the original state, and with
ALTER DATABASE database name DROP FALLBACK SNAPSHOT
you can remove it, and you can query the monitoring view M_SNAPSHOTS
to find out if any snapshots have been created.
This is all documented in the SAP HANA Administration Guide and the Tenant Databases guide
(same text) under Create a Fallback Snapshot.
That’s it.
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