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When an SQL Server RDS instance provided by Amazon is configured for a recovery model using Full transaction logging, will the transaction log be trimmed by the "transaction log capture" that Amazon performs every 5 minutes, or is this capture not a true transaction log backup?


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Almost certainly it does trim the transaction log. (Otherwise the Amazon cloud will fill up with transaction logs.)

Some details from the Amazon site include this topic and two sub-topics that you can investigate:

When you create a DB instance, you are assigned to the db_owner role for all databases on that instance, and you will have all database-level permissions except for those that are used for backups (Amazon RDS manages backups for you).

For a discussion of the backup model and how you influence it, see:

And, of course, if you change the model from FULL to SIMPLE, the retention period, and so forth that will affect your restore points.

Amazon definitely support point-in-time restores, which means that the transaction logs are being used. But since they do this for all database server types that they support, I do not know the mechanics of what they use to do this.

On the restore process described here:

When you restore a DB instance that is using the SQL Server DB engine to a point in time, each database within that instance will be restored to a point in time within 1 second of each other database within the instance. Transactions that span multiple databases within the instance may be restored inconsistently.

So I would say that, whatever the mechanism of the log backup, it will be available within the constraints discussed in their documentation.

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yes it does and it depends on the retention policy which is user configurable Amazon RDS retains backups of a DB Instance for upto the last 35 days (configurable) – Kin Sep 5 '13 at 15:04

From, Amazon RDS FAQs, the "transaction log capture" will allow you to do a point-in-time recovery of your database.

The automated backup feature of Amazon RDS enables point-in-time recovery of your DB Instance. When automated backups are turned on for your DB Instance, Amazon RDS automatically performs a full daily snapshot of your data (during your preferred backup window) and captures transaction logs (as updates to your DB Instance are made). When you initiate a point-in-time recovery, transaction logs are applied to the most appropriate daily backup in order to restore your DB Instance to the specific time you requested. Amazon RDS retains backups of a DB Instance for a limited, user-specified period of time called the retention period, which by default is one day but can be set to up to thirty five days. You can initiate a point-in-time restore and specify any second during your retention period, up to the Latest Restorable Time.

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I've read that description but was uncertain if what Amazon calls "log capture" has exactly the same semantics as a log backup (incl. leading to the log being trimmed; my key concern here) as described in an SQL Server context. – Cumbayah Sep 5 '13 at 19:13
@Cumbayah It is exactly what it says. It will allow you to do a point-in-time recovery as well it has a limit of 35 days that you can keep worth of. So depending on your need, you can trim/get rid of older ones. – Kin Sep 5 '13 at 19:14

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