Why am I seeing an Emergent Snapshot or my snapshot running after my backup window is closed for my Amazon Relational Database Service (RDS) for SQL Server instance?
An Emergent Snapshot is an automatic as-needed backup taken by Amazon RDS due to the following:
- Restoring or creating a new database with SIMPLE recovery model.
- Modifying recovery model from FULL to SIMPLE/bulk-logged in both single and Multi-Availability Zone (AZ) instances.
- For Point in Time Recovery (PiTR), RDS uploads transaction log backups every five minutes for DB instances to Amazon Simple Storage Service (Amazon S3). When RDS doesn't take transactional log backups successfully, an Emergent Snapshot is triggered by RDS to mitigate problems during PiTR.
- After instance patching is complete, RDS triggers an Emergent Snapshot to safeguard the instance.
You can back up your Amazon RDS instances using one of the following methods:
- Manually back up your DB instance by creating a DB snapshot. For more information, see creating a DB snapshot.
- Automatically back up your DB instance by making sure automated backups are turned on. Amazon RDS creates and saves automated backups during the backup window of your DB instance.
When manually or automatically backing up your DB instance, an event "Backing up DB instance" is logged in RDS Events. Automated backups occur daily during the preferred backup window. Also, observing an event "Emergent Snapshot Request: Databases found to still be awaiting snapshot" in RDS events creates an automatic ad-hoc backup. This automatic ad-hoc backup occurs outside the instance backup window.
Note: An Emergent Snapshot is normal and is an expected behavior.
To identify the reason for Emergent Snapshot, review the SQL Server engine logs:
- Open the Amazon RDS console.
- In the navigation pane, choose Databases.
- Choose the name of the DB instance that has the log file that you want to view.
- Choose the Logs & events tab.
- Scroll down to the Logs section.
- (Optional) Enter a search term to filter your results.
- Choose the log that you want to view, then choose View.
Review the Amazon RDS for SQL Server logs, which are logged immediately before the Emergent Snapshot, to identify messages similar to the following:
BACKUP failed to complete the command BACKUP LOG Test_Database. Check the backup application log for detailed messages.
Setting database option RECOVERY to SIMPLE for database 'Test_Database'
Restore is complete on database 'Test_Database'. The database is now available.
Starting up database 'Test_Database'.
The Amazon RDS for SQL server logs indicate log backup failures and changes of a database recovery model to SIMPLE. They also indicate new databases restored on an instance or new databases created.
To identify instances that have been patched, review RDS Events to look for an event similar to "Applying off-line patches to DB instance".