Why do I see Emergent Snapshot or a running snapshot after the backup window ends for my Amazon RDS for SQL Server instance?

Short description

An Emergent Snapshot is a normal and automatic backup event that Amazon RDS takes when the following occurs:

• You restore or create a new database that has a simple recovery model set.
• You modify a recovery model from full to simple or bulk logged in both single and Multi-AZ instances.
• Amazon RDS didn't successfully take transactional log backups.
  Note: Amazon RDS creates an Emergent Snapshot to prevent issues during a point in time recovery (PITR). Amazon RDS uploads transaction log backups every 5 minutes to Amazon Simple Storage Service (Amazon S3).
• DB instance patching is complete, and Amazon RDS created a snapshot to safeguard the instance.

To back up your Amazon RDS instances, take one of the following actions:

• Create a DB snapshot to manually back up your DB instance.
• Turn on automated backups for your DB instance. Amazon RDS creates and saves automated backups during the backup window of your DB instance.

When you manually or automatically back up your DB instance, Amazon RDS logs a "Backing up DB instance" event in on the Events tab. Automated backups occur daily during your preferred backup window. It also logs a "Databases found to still be awaiting snapshot" event when Amazon RDS takes a one-time backup outside of the instance backup widow.

Resolution

To identify the reason for the emergent snapshot, review the SQL Server engine logs that Amazon RDS logged immediately before Amazon RDS created the snapshot.

Complete the following steps.

1. Open the Amazon RDS console.
2. In the navigation pane, choose Databases.
3. Select the DB instance that has the log file that you want to view.
4. On the DB instance details page, choose Logs & events.
5. In the Logs section, select the log, and then choose View.
   Note: You can also enter a search term to filter your results.

Review the Amazon RDS for SQL Server logs that are logged immediately before the Emergent Snapshot occurs.

The logs contain messages that are 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'."

To identify patched instances, review RDS events to look for an event message that's similar to "Applying off-line patches to DB instance."